SCBA (without the U) is what Fire Fighters use, not divers. Different fittings (indeed different series). One option is to buy the adaptor so the DIN fittings (not CGA like on your tank) the Dive Shops use will fill your tank. However most dive shops can't fill much past 3000 PSI (standard for SCUBA), I'd call and check if you can get 4500 PSI fills from them.
Otherwise, the Fire Fighters have to get their tanks filled somewhere (it's a cinch they don't ship them 'Stateside'....). I'd ask around. Some Fire Houses have compressors, some will fill 'out the back door' (proper payment is Rocky Road ice cream....all FF seem to like it....save the doughnuts for the cops). Otherwise, perhaps they can steer you onto a shop that can take care of you?
Good luck, it's worth the effort. Once filled, that tank will recharge your Marauder 100 times or so with 30 or 40 shots per charge.