5/8x24 is a standard thread for the AR platform, so you have a ton of choices avail. You just need to decide, are you looking for a brake/compensator or flash hider?
The big trick is finding something with the same or as close to the same O.D. as your barrel, so it doesn't look out of proportion.
Some of the ones i've seen cross- over from ARs' onto rifles are (prices listed for under $100 requirement);
PWS FSC 30
PWS Triad 30 ($82)
Vltor VC-301 ($69)
BattleComp BABC
The Miculeks' can be ordered from Brownelles or thru a local gun shop who has a FFL account with Brownelles. Not all of the Brakes or Comps however can be exported as they are ITAR regulated. Brownelles is usually pretty good at listing in the item details if they are able to accommodate foreign sales of a certain item.
Mystic Precision hasn't had the Miculek or JP Enterprise Bennie Cooley Comps for about a year now.