Goblins! I made a fuel cell one for you at one point... :)
there is also the official Sealed model which has a SFE. though it has some of the same budget issues as the fuel cell Bulldog.. it uses a SnubPPC, which combined with the SFE drives the cost up a lot. (and it loses the infantry bay) it's also not really widely available.. fedsuns, lyurans, mercs, and some of the new former JFOZ groups.
hmm.. perhaps they could make use of the Pike? how are their relations with the Magistracy?
edit: with a fuel cell and environmental sealing, the pike is 1/2 ton overweight. perhaps they could adapt the AC5 variant, and drop the AC ammo down a ton to fit? boosting the armor with the remainder