Just check the EE. That's where I got my PWA A1 style rifle. Upper was from a military spares contract, bolt and carrier were pure Colt M16. Buttstock was M16A1 as well. Had to add a couple of items to make it more authentic, like the triangular handguards, proper pistol grip, etc...
If you look in the EE there was just such a rifle not too long ago, seller described it as an A2 but when the pictures showed up it was an A1 upper.
Since these aren't really that popular they can be fairly cheap compared to other rifles, I picked mine up for less than a grand, saw one for $850 not too long ago if I recall correctly.
I do agree with RobAK though, not a better infantry weapon. Simpler, lighter? Absolutely, but better? No. Lights, sights, lasers and railed forends are often neccessary and mandatory on an infantry weapon.