Most any factory made part from Ruger and Smith & Wesson (and Colt) is available from
Brownells. If I were you I wouldn't worry about it to much tho. 1) Revolvers from these companies are very stout, barring massive neglect on your part, it is doubtful you'll ever have a failure of any kind. 2) If anything did ever break, bend, bust, fail, or fall-off... Ruger or Smith will fix it free of charge. I've sent old pistols I bought used to both companies for repair. In each case the pistols were fixed, parts were replaced, and the gun returned with a little note saying "no charge". The fact that I was not the original owner and the guns were 10-15 years old didn't seem to matter.
Regarding the 686, excellent choice. In fact I bought one today at a gunshow. 3" barrel, round butt, adjustable sights, and a bead blasted matte finish - $439 NIB. The sign on the gun said "1 of 500", so apparently it's some kinda special run or something. Fine with me, I've been looking for a 3", round butt, with adjustable sights for some time. Was looking for a model 60 or used 66, but this will do. It even came with a trigger lock, something Smith has been putting in with all their new guns since sometime in '98. -- Kernel