They are sold at both Apex Gun Parts and at AIM.  This is the description:

Exact copy of the Bulgarian four piece flash hider. This is the best, most affective muzzle brake ever made for the AK type rifle. It is threaded for the 24x1.5 threads. It can be used on the 7.62x39 rifles with the use of a thread adapter which we sell.

Anyone try these?  I tried a search.

I think the AIM version is made in China. I would stick with the Bulgarian versions as the cone is chrome lined.

Link? (you pic is dead @ 0808 19oct08)

If it's the one I think it is then it's not actually a brake, it's a back pressure enhancer for Krinks. They also redirect blast from short rifles forward so as not to destroy your ears instantly.

If you need more pressure I'd get the real one. I've heard the AR SBR guys that use them a lot have had to replace cones due to erosion. Hardchrome would stand up better to that. BSW