How do I confirm hubcap fitment BEFORE ordering online?

I'm looking for a set of dog dish center caps (poverty caps) for my steel wheels when I have my winter tires on, I'm sick of the cheap plastic ones cracking and breaking apart after a few months, and I don't want to use my good hubcaps in the winter out of fear they'll be damaged if I hit a curb. I need a set of tin center caps for 15" steel wheels, I figured old police caps would work well, but they're too expensive. I've found some cheapie "universal" center caps on ebay here and there, but I'm having a hard time figuring out if they'll actually fit or not. Is there any way to actually confirm if they'll fit for sure or not, before I order? Or do I just have to start ordering parts and keep trying until I get the right ones?