I don't throw things away either. That just means they go to a land fill where they'll stay virtually forever and be of no use to anyone. I take them where they can be recycled.

Your pump isn't perfectly good. As evidenced by your need to find a new O-ring. And in todays consumerism, sometimes just getting a new thing, and properly disposing of the old is the better thing to do.

For certain there probably is a O-ring for it. But are you certain the O-ring is the only thing wrong with it. Check valves and other methods of letting supply or new air get into the pump cylinder as well as keeping air already pumped into tires with Schrader valves can be at fault to. Many of the good brands of pumps offer rebuild kits. But Schwinn is long out of business. At least as it was prior to the mid 1990's.

But if fixing it is what you want to do, there is no need to get all high and mighty sounding. As you can see, I do that well myself.

If you are in a area that has a lot of industry, then there are likely suppliers for that industry there that will have all sorts of O-rings. Granger might be one of them. But whether they'll have staff that want to hunt for hours for a single O-ring that only cost them ½ ¢ or less is another question.