So, if you want Larue it’ll be tough to find a matching lower as not many companies are building in that pattern, so you may be looking at a complete rifle. If you would like to build, which I encourage you to, then the Aero sets are not only budget minded but pretty nice. Mega Maten sets are gorgeous, I have one I’m building up, and offer full ambi options. Using quality parts in the heart of your rifle (barrel, bcg and trigger) is where you will find accuracy.
Armalite and Matrix are the only ones I can think of using that cut. Knight’s are too now that I think of it.