Does anybody know where I can get new strings for this thing? I have no idea what the gauge is, and it's such an uncommon guitar that the shops around here have no idea what would work. Any advice?
I use plain old 13-56 on my Epi LP baritone. My guitar has a 27.75" scale, and I think the 2 recent Fender Jaguar baritone models have slightly different scales from mine and from each other. Still, 13-56 would be worth a try. If you find those gauges to be too heavy, you could try 12-54, and for heavier gauges, check the D'Addario website.
You might want to measure the string holes in the tuners first! I went 10-68 on my cheapo seventstring, because a 0.070" was the largest diameter that could be forced through the tuners. YMMV.
25-95 sounds pretty freaking heavy. Keep in mind the old Bass VI, the Baritone Custom with 2 single coils, and the Baritone Special with 2 humbuckers each have different scale lengths. If those 25-95 strings fit on one of the baritones you are talking about, the notes would probably be an octave lower than what I have.
I have recently switched to Ernie Ball 12-56 gauge for my 27.75" Les Paul and for my 25.5" Telecaster, both in B-standard tuning. When I first got my Ephiphone baritone, I tried some 25-95, I think, set, and the tension was a little hight than I would have liked it to be. Fooe free to experiment, yo.