[brucepick]

If you can find an "automotive recycling facility" (aka junkyard) you should be able to weigh a rim. There are self service yards in some areas where you can scrounge around to your heart's delight. Or you will have to make do with a "full service" yard where they bring you what you ask for.

In either case, go with sturdy work clothes, solid footwear and a scale. A jack and tire wrench (or breaker bar with sockets) in hand will show that you're ready to go.

Many yards pull wheels for future sale and stack them by brand/size, with tires removed.

Get one from your make and model, similar year, and weigh it.