I have a slabside Colt SP1 upper which does NOT have either the forward assist or the brass deflector bump. It has a semi-permanently installed adapter bushing (it can be removed without damage, it's just loctited in)installed in the front takedown pin hole for use with standard push pins. It's in very good shape, with original finish.
This sounds like what you're looking for, or pretty close, anyway. If you want to build up a "vietnam look" early model rifle, this is the thing.
I'll trade even for an A2 upper in good shape.
I will also throw in a set of A1 triangular handguards (the right one has a crack in it near the front edge but it's not bad) and an A1 buttstock with the semi-smooth, rounded edge buttplate, but it does have a trapdoor in it. That should be a later type A1 stock. It's close...but the stock and guards are not new. They are used but in pretty good condition.
My A1 upper is currently installed on a good shooting rifle. So don't take the offer if you're not serious. I don't want to tear down the upper and end up having to put it back together.
Both my A1 and your A2 upper will be complete, that is, including sights, ejection port cover, etc.
CJ