I have a nice early Colt A2 CAR upper with M4 ramps.  I can't find a Colt A2 rear sight assembly.. 

Any help appreciated.  

RRA parts schematics look like the ones LW Schneider makes for Colt.  If I can't order the assembly from Colt I guess I'll have to entertain other options. I priced the parts from Brownells which are out of stock, and it totals well over $200.00 which sounds crazy to me.  I also need a FA, and Dust Cover Assembly, and CAR lock ring, at the moment.  

Shop the EE. There is a member selling A2  rear sights currently  (not sure of manufacturer) and
I see the other parts you mentioned from time to time.

Also, Brownells carries Colt branded forward assist and port cover parts,  if I recall correctly.

Just keep checking the EE for AR15 used upper parts. I'm sure a rear sight assembly will show up sooner or later.
I've been going to every local gun show for the past year looking for a Colt side sling swivel for my 6920, and never found one.
The first day looking on the EE, I found one for $25.
Everything turns up there eventually, just be patient.

I probably should be on the Misc. EE also.  Thanks for the heads up.  I wonder if anyone can confirm that RRA is made by LW Schieder?  If so I'll just order a set from them.

I got a couple from Sarco Inc. They seem to be all over the place as far as condition of the parts, but both of mine were new in wrapper. I don't know who made them though.

http://www.e-sarcoinc.com/ar15m16a2rearsightassemblyusedexcellent.aspx

A big thank you for that link.  I ordered what I needed, and I'm good to go now... They're military surplus according to Sarco so that's good enough for me. (The windage knob has the Colt line in it, and the aperture looks Colt)