Latch only or entire lockset?

Your handle set isn't made anymore, but I've known other customers who used our 40-150 as a replacement for the older inside latch. I think this is your best option. The only caveat is that you will likely have to shim it up a little to meet the old keeper.

If all fails, though, then I do think that our 40-177 can be used as a substitute.

Both the 40-150 and 40-177 can be flipped around to work on either side.

Yes, the 40-177 should come with all the proper spindles and hardware for installation. As for shimming the latch, we actually did carry a shim specifically made for the 40-150 at one time, but it was recently discontinued and we have been unable to find a good source for something similar. I would check with a local hardware store and see what they recommend. You could potentially use washers but that's obviously not very good looking. Hopefully a store near you has a plate of some kind that can comfortably mount under it.