Are they made yet?  Where can I find one?

None that I'm aware of, but it maybe possible to re-thread a Vortex or a YHM phantom to HKs 15X1mm threading. I'm about to send Jayson at IGF and email regarding this and possibly re-crowning my V93s barrel. It might also be a good idea to contact Vector and see if they have an american made FH since the ban is done for now.
I'll post any responses I get.

C

****Update****
Jayson is working on a Flash hider for the HKs, but it will be a few weeks before they're ready.
IGF does have a birdcage brake that looks just like the FH. Check it out.
IGF products page

Thanks.

I found a guy who's selling Smith enterprises Vortexes that he claims fits the HK threading. A bit pricey [$140]though.
His thread is over on Hkpro.com, just do a search on the marketplace for 'vortex'. The only other option would be to get a four prong from Cals or HKpartsonline.com. Neither will help you parts count if you're already at the max.
I'm probably gonna wait and get a birdcage type from IGF when they're ready.

A Smith Enterprise Vortex cost $45-75. Right now they are backed up two months with US military oders.  Send them an email and they will respond.  $140 is a rip off.