Well this turned out to be complicated. Thanks for all the advice. I use my avatar and it's important that the bobbins fit on the winder. Annette said that Bernina ones won't fit, so that's out. I tried to find 2518NS bobbins but could not. I found tons that call themselves "2518" but I think the quality may be variable. Cindy Peters on ebay is not selling any longer. I'm wary of the ones sold by just anyone on ebay - they could be the same garbage I'm buying at WalMart. I did see some on ebay called "vintage" but they were quite pricey.
I've been too busy lately to hit the brick and mortar stores but I had a little time to do some online shopping.
I ended up ordering 2 different sets from Amazon. I ordered the ones that were "for Kenmores" which ClairVoyant recommended. I also took a chance on a set of 20 on Amazon for under $2. They got mixed reviews. If I am happy with either set, I'll order a lot more right away so I don't have to do this again!
NJQuilter, I may take you up on your offer of testing your bobbins in my machine next time we get together.