Oh, so that is what the sheet feeder is for! I see them on ebay fairly often and they sell for semi-high prices. I thought it had something to do with feeding a larger amount of paper at a time.
I was checking Amazon and some other office supply stores and it seems you can readily get tractor feed paper but you have to buy an enormous box (2300 sheets or more) for $30-40, I didn't find anything smaller. (One cheaper $18 1000-sheet source on Amazon but some reviews complain paper is too thin.) Still, that would probably last me the lifetime of any of my dot matrix printers and beyond. I haven't gotten around to getting any of my several dot matrix printers running.