Yeah, that's the way I thought that I'd make one if I'm going to get the winch.
That part seems to be discontinued, but if you are lucky you might find one from ebay or somewhere. I used "dodge ram spare tire winch hex shaft" when I googled info, and found couple shafts for a Dakota, but not for 2nd gen Ram.

 

I believe there are two different length tubes for the 2nd gen truck, depending on the length of your truck bed (6 foot or 8 foot). I ran into the same issue of needing one a while back and ended up finding one at a local junkyard.