What sort of names are you looking for? For Holden, I mostly used the fictional Saturn-based company known as Dodekatheon Industries, which makes Orbitals and equipment for Orbitals based off of Greek Mythology. There's also Colonial Arms, which I imagine is basically not!Colt, which produces rugged, but reliable weapons for use on the ground. 

I've also noticed that some of the mechs or equipment used by the other characters occasionally share a manufacturer (i.e. Jawaid & Jawaid Industries, the Ajax and the Odysseus, etc), which I think was really cool. Maybe you could borrow some of those, if you like. Otherwise, I could probably come up with a set of generic corporation names that you might find handy.