I have an old S&W 66-1 that had a screwed up rear sight.  The blade was dented up pretty good and  the adjustment screw was broken.  I got the gun in this condition and that was the only problem.  It's a 66-1 that's pinned and recessed and I got it cheap so I can't complain.  

Last week I got new S&W parts, the blade, the screw and the windage nut on the other side.  There was no detent ball in the existing screw when I got it apart.  Does anyone sell that part?  It's usable now if I run the windage nut down tight and stake it after I sight it in and it will have what amounts to a fixed rear sight.  But if I can get the detent ball I will.  

Thanks!

I think Brownells has these parts...just installed a new screw and all the goodies ball/spring etc.

Supposed to use a new screw anytime you take these apart.

Midway has them.  The same spring and plunger is used in the elevation screw.

Midway:
http://www.midwayusa.com/product/924364/smith-and-wesson-rear-sight-plunger-s-and-w-14-to-19-24-25-27-28-29-34-36-57-60-4-63-66-67-317-325pd-329pd-500-586-610-617-620-624-625-627-629-631-648

http://www.midwayusa.com/product/961206/smith-and-wesson-rear-sight-plunger-spring-s-and-w-14-to-19-24-25-27-28-29-34-36-57-60-4-63-66-67-317-325pd-329pd-500-586-610-617-620-624-625-627-629-631-648

Also:

http://www.jackfirstgun.com/

Great, thanks!