I have looked at few bolts for my IUR,
My friend's LMT enhanced, very good, one thing I didn't like is the BCG's finish felt like sandpaper.
COLT USA, mil spec, nothing fancy but I'm sure it works.
I really wanted the LWRC enhanced battle bolt, but that thing cost $300USD just for the Bolt alone, no BCG.
finally, totally unexpected, I found a PWS enhanced DI bolt, CNC machined, built like tank, better super hard coating(Isonite Treated), weights a little more than a full-auto bolt for extra reliability.
tested it out in my friends AR before putting into my colt(i'm evil , worked fantastically in both guns, both rifles used H buffers btw. did I say this bolt is built like a TANK!
not my pic, shamelessly stole from the internet.