I converted to 12v and am now using an alternator. Unfortunately, I havn't seen any alternator-p/s pump combos. The closest I've seen is the Izusu alternator-vacuum pump combo for the diesel engines.

'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi