Jack, here's a link to one such source.
http://www.coltparts.com/pt_51navy.html
Whether or not you buy from them is up to you. But at least it will identify the nomenclature and location for ya... :wink:
Definitely stock up on the hand/spring assembly (#10 on the '51 Navy) and possibly the bolt as well (#4 on the Navy). Also the trigger spring (#25). I've broken hand springs in two out of my three revolvers with only a few hundred shots through them. It will certainly ruin your day.(Which is why I have three revolvers...) :hmm:
I've not broken a trigger spring yet, but they look pretty flimsy. The bolt is the one part that will wear quickly as it comes into use with every lock-up of the cylinder.
The cylinder, is of course, hardened, so in most instances the bolt is not.
One thing I've noticed on these repro's...as tempting as it is, don't go all Dirty Harry and put it on half-cock and "whirr" the cylinder. It's boatloads of fun, sounds cool and looks impressive. It also leads to broken hand springs shortly after such episodes. I'm not sure why? :idunno:
Normal cocking of the action does not seem to affect this.
What make/repro are you shooting? Maybe I can help you track down parts.