I have a challenger panel with a burned bus and bad breakers. I'm looking to replace them. I called my local shops and they said they don't carry this anymore. Is there a replacement option without going to remove the entire box? I am mainly looking to replace the interior components Bus and breakers. I don't mind other brands as long as they fit. The panel is 100 amp and I have attached images of the label and the bus. Thank you. 
Electrical – Challenger Bus panel
circuit breakerelectricalelectrical-panel
Related Solutions
You can use BRs instead of Cs
If your panel labeling says it takes type C breakers, then there's an easy way out of it: type BR breakers (as depicted below, with the type C labeling highlighted) are legal, safe, and widely-available (at any big-box or hardware store) replacements for type C breakers, as they are cross-listed (as per this letter from UL to Cutler-Hammer, as reproduced at the bottom of this post) and cross-labeled to replace type C breakers. (A more modern version of this letter is available, linked from an Eaton FAQ.)
For more exotic Challenger breaker types, Eaton cross-reference document TD01201041E provides the gory details.
Stop faffing with the Challenger breakers, pull out the bottom right 15A breaker, and install a BR115 bottom left and a BR240 bottom right
Buying "new old stock" or newly made Challenger-style (UBI/Connecticut) breakers is an expensive and frustrating exercise, so why are you insisting on trying to go through it? Eaton BR breakers are cross-listed and cross-labeled as type C (or type A for BD/BQ tandem/quadplex breakers) and can be safely and legally used in Challenger panels, as per this letter from UL to C-H (and see my answer here for more details); never mind that a BR240 is $10 and available anywhere in the USA, while the 40A UBI Challenger-style breaker is $50, harder to find, and probably not as good as the Eaton breaker (UBI seems to have...issues with breaker QC and QA).
If you really insist that the bottom left slot stay free, you can get a single, quadplex, BQ2402115 breaker and use it to replace the 15A breaker bottom-right as well as provide the new 40A circuit and a 15A spare. This is costlier than using the two full-size breakers, but still more reliable than the UBI breaker, and no costlier than the UBI part for that matter.
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Best Answer
Haven't heard back from you, so here goes.
About the panel/breakers
This thing you have is a meter-main with 12 breaker spaces. The main is "backfed" meaning the main breaker is just one of the breakers.
The Challenger breakers are known to be defective. And because of that, many electricians treat Challenger panels as if they're defective. They're not. There's nothing wrong with Challenger panels. The breaker problem can be very easily solved: Eaton "BR" breakers are cross-listed for it. Take a look at any BR breaker, it says
Type C is for your panel. Ba da bing! That's easy.
By the way, if the home inspection report had said something about that and you said "meh, whatever", replacing those Challengers with BRs would have prevented this. So next time you see something like that on an inspection report...
About that bus
Your plan, as you have presented it, is to "just replace the bus" using a components supply chain that does not exist in real life. This brand has been out of production for 30 years. Compatible buses go in the trash every week, but nobody thinks to upcycle them onto eBay or Craigslist becuase they are obsolete and connecting with a buyer is extremely unlikely. There are companies that specialize in old Challenger panels, and you can try, but this is an odd duck even among Challenger.
So replacing this bus is not gonna happen.
As far as finding a modern bus that will fit, the problem is panels of this style are also obsolete: the very compact buses and gutters are now illegal due to "new" rules regarding wire bending radius (see that neutral wire for why).
So fuggedaboutit. You only have 2 options: Save this bus or replace the entire meter-main assembly. Chassis and all. I'll talk about saving this bus.
Saving the bus
The bus position containing the melted breaker (9-12) is permanently useless. So now we have two questions:
Either way, we are going to change all the Challenger breakers here for Eaton BR/C. The Eaton BR2100 ought to do the trick, at $40 each. Betcha didn't think you could get out of this for $100, did you? :)
If all busing is in good shape
In this case, we leave the main breaker at its position, and fit the feeder breaker in positions 13-16. The cable will reach. Easy peasy!
If the bus below space 9-12 is fried, but the main is OK
In this case, we leave the main breaker where it is. We move the feeder breaker to positions 5-8. Any remaining breakers go to positions 1-4; no breakers exist below the main. This will involve extending the feeder wires; pull new wires if they're short, otherwise extend them with insulated Polaris lug splices.
If the bus under the main is roached
In this case, you will need to remove the bus bars which come off the meter socket, and replace them with #3Cu XHHW wire. This will need to be physically protected where they come through the hole.
The main breaker is then moved to spaces 13-16 (below the melted breaker), and it will need to be bolted down the same way it's bolted down now. The feeder breaker is moved to spaces 17-20. That leaves spaces 21-22 for anything that is now above the main breaker. Remember this panel permits "BR/C" duplex or quadplex breakers, which you can put in spaces 21-24.