Oh, buddy, you own an Emco lathe and high dollar is something you'll have to get used to. Parts are no longer made for these lathes and you are competing with the rest of the Emco-owning world for those parts. Many parts can be made but some, like the hardened and ground spindle and gears are better found on the used market. Do yourself a favor and find the complete change gear set; you won't use it often but when you need it, you need it.
Once upon a time, Emco made their own chucks but they eventually just got them from Rohm. I am not sure about the V13 but since it came along after the Super 11 then there is a very good chance your lathe chuck is a Rohm chuck. If so, you would have a hard time finding a better one. I own two 3 jaws, two 4 jaws for my Super 11 - all Rohm chucks. I own two of each because a different version from the usual OEM version was available at one time and it was a forged version (I think) of much higher quality and with different construction. These chucks were expensive! Regardless, Emco did not use cheap chucks. In fact, they did not use cheap anything.
Here's some advice. Look for and buy a spare cross slide nut and leadscrew and tuck it way somewhere. One day, you will be glad you did.