I might be missing something on the new technology front, but the only standard form battery with snap-on terminals I've noticed is a 7.5V, not 9V. You can get a new snap with longer pigtails at Radio Shack for about $1.39 (US) if that would help.
I haven't seen rechargeables in the standard 7.5V form, although they might be available. We do have lots of "battery sellers" who claim "If we can't get it we'll build it for you," so you likely could get them to find or jury-rig something for you. Lots of the $65 phone batteries consist of about 4 (you'd need 5) 1.5V 1099(?) or 1035(?) NiCd "watch batteries" ($1.25 each?) crammed into a piece of shrink tube and then smeared with some RTV bathtub caulk to keep the wires from wiggling. Of course you'd have to find (or make) a 7.5V charger (Or a 9V if that's really what you've got.), or cannibalize a cordless phone stand for the charger - or somethin'.