indian-cuisine
Normally one is to get a piece of charcoal red-hot, put it in a small metal cup, put some ghee on it to burn/smoke, and put it in the pot with the finished dal tadka curry.
I don't have charcoal. And even if I bought charcoal I don't have a gas burner to heat it. I have IH burners (electric induction heating, which can't heat charcoal).
Main ingredient for making a traditional dosa is rice. Rice can't be substituted. Although you can definitely reduce the amount of rice you are using.
From what you've mentioned, you are using 3:1 rice to black lentil ratio. Using 2:1 rice to lentil ratio can also yield you similar batter without compromising the crispiness.
I am assuming that you only use rice and black lentils. You can try adding more types of lentils like Moong (Split Green Gram lentil with skin removed) or Toor Daal. The point here is to reduce the amount of rice in per serving by adding lentil. I usually follow 4:2:1 rice to black lentil to Moong Daal ratio.
If you completely cut out rice, you can still get similar crepes using substitutes but they won't be authentic dosa. You can try Rava Dosa (Semolina Crepe) or many other substitutes mentioned here
If the bhajis fit into the toaster slots, toaster bags should work. They are primarily intended for toasted sandwiches, but it they can contain melted cheese good I wouldn’t expect a bit of bhaji grease to be a problem. They should work for samosas too.
Most supermarkets sell them, there are lots of brands available on the High Street or online. 
Best Answer
Smoked salt for general use in kitchen to get "smoked/grilled" taste or for dal tadka smoked chilli pepper. Latter is no so strong as normal chilli (so you use more) but give nice aftertaste to spiceness.