I wonder which guide the Kodiak will show up in. Also wondering who's going to wind up producing the Masakari: here's hoping it's not the Sea Foxes.
I think the Sea Foxes are the most likely source. The Ebon Jaguar, Iron Cheetah, Huntsman, Shadow Cat, Shadow Cat III, others... they make enough stuff one more doesn't seem impossible. I'll grant they'd be a boring source, and i'd imagine their current products are stretching their manufacturing capabilities as it is.
Figure the Hell's Horses may be potential source as well, as it is they've either captured Wolf production facilities or put old 'Mechs like the Mad Dog and Dire Wolf back into production. The biggest question is if they'd need/want another assault 'Mech.
The Republic of the Sphere could have been making them, for the Fidelis, though i suspect any source is very new, after 3145. And don't think the RotS would've created a Warhawk factory this late.
I regard the source being the Scorpion Empire to be unlikely. That the Scorpion and Goliath OmniMech projects seem to be unfounded rumors in opinion of Sea Foxes makes me skeptical they'd be manufacturing Warhawks either, especially if the Snow Fox OmniMech is just a pilot project (though i suppose that could've meant pilot project for OmniQuads than OmniMechs in general). Seems to me that any contact they may have is very limited, and thus trading OmniMechs seems unlikely. (Also figure these tidbits about the Scorpion Empire are building for some stuff in the future more so than them being involved in IS affairs in any way right now.)
Though very unlikely, it would be amusing if the Warhawk was produced by Assault Tech Industries in Donegal. The Lyrans have good grasp of ClanTech, with or without help of Wolves-in-Exile. And the Warhawk is big and imposing, though admittedly faster than typical Lyran preferences ;D
Figure other options, be they Clan or Spheroid, are less likely than the ones i laid out above.
Of course, there's always a possibility of more than one source.