Just so you guys know.. I'm not sure Igo's actually deals with small tanks and/or they're accessible w/o a car.
There IS a place in Boston near Skipton's... a couple blocks from Skipton's.. where we get my tank filled up.
I would say, call Skipton's and see if Aric or Steve is there. Either of them would probably know the name of the welding supply place that is near them.