You won’t find a repro brake booster to replace that, assuming you are going for a stock replacement.

I would suggest you get a hold of Wayne at the RamMan Inc. He rebuilt my Hemi booster, did a great job

'69 Hemi Charger 500, ‘70 U code Challenger R/T
(These and a bunch others at www.dkowal426.com)

P.J. O'Rouke: "The old car ran perfectly, right up until it didn't."