I'm using an Airsoft one from G&G. My gunsmith couldn't believe it was an "airsoft" part, so that says something. And yeah, EE here is for Canadian citizens only; kinda frustrating trying to find a C79 or Eickhorn bayo for less than insane prices but with ITAR crap I understand why they do it. Their house, their risks if something goes sideways.
https://101techusa.com/tri-rail-mount-black.html Reach out to these guys as a temporary stand-in; Mike there arranged an end-user sale for me.
EDIT: Here's that rail on the girlfriend's C8 -think we've discussed this build before here and at M4C.