Well, if you're looking for a long flash hider, the L1A1 FAL hiders are rather nice (and we have one member here with one on a CETME, but he bought it with it already threaded on). I also like the tabuk/SVD AK-variant flash hiders and bought one for my AK-variant. They can be had from
nodak spud, in the white, so you have to finish them... I parkerized mine.
The FAL hiders can be purchased on-the-cheap from gunbroker.com, but if what I think you're saying is what you're saying, then you don't have any threads on the end of your barrel and you'll have to thread the barrel no matter what you go with. This is really your best option (and make sure you have a reputable gunsmith do it) as that will keep the hider in-line so that bullets don't glance of it and cause damage. That's been known to happen with clamp-on styles of hiders, such as those for the AK-variants.