Doors – find replacement double action hinges for an old, heavy door

If you're in an area with older homes, try your local locksmith.

The last time I had to replace a split spindle (where the split was not in the middle), the local lockmith had 'em in steel and brass. I went with the brass, because I had to grind out a channel so it'd fit into the existing mechanism; you might have to do similar and drill it yourself.

The ones you see online probably aren't a press fit -- most of my knobs take a set screw.

You can also try a real hardware store (not a Lowes or Home Depot ... either an independant one, or an Ace, True Value, etc.)

If you strike out completely, I've also replaced the whole knob and spindle with a replacement set, and switched to a threaded spindle. It looks like Van Dykes has a few :

• http://www.vandykes.com/product/2-glass-knobs-with-spindle
• http://www.vandykes.com/product/glass-knob-and-spindle-set
• http://www.vandykes.com/product/glass-door-knobs-with-spindle

It looks like what you're looking for is referred to as a 'drilled spindle' (possibly drilled & tapped, if there's threading inside the holes)

Using the search "drilled door spindle", I've managed to find a shop in the UK:

• http://www.doorfurnituredirect.co.uk/scpro/bernards/productscategory~prodtype~58~prodtypename~Spindles.htm

... but many of the hits talk about pre-drilled doors, rather than specificall drilled spindles.

A quick trip to Home Depot or Loewes will find you a selection of similar door knobs with locks that should fit into exactly the same fitting.

You'll find either the ones that lock when you're inside, just pressing the button, or ones that take a key in the centre of the handle.

It should be a simple matter of unscrewing and removing both handles, and sliding the new handles in place through the existing bolt mechanism.

I've replaced a bunch of door handles that way, both locking and not.

Something like this: Locking door handle, and only $15.