I would bet on Savage/Stevens/Springfield, but I doubt you will have any luck in any case. I think everyone who ever owned one of those guns lost the magazine. The original makers are either out of business or long ago ran out of spare magazines and aren't going to make any more.
At one gun shop I worked at we quit even trying to order magazines for those shotguns; we just told the customer they were not available. Otherwise, we would spend hours in searching and lots of money in stamps for something that, if we could locate it, would give us a whole $2 in profit on the sale.
You might get hold of the Gun Parts catalog, try to find the gun that looks like yours, and see if magazines are available.