Center hub caps

[AA-ron]

I'm not going to use the knock-off spinners on my build, and instead I'd just like to use a center cap cover the opening. My wheels are the 18" Halibrand style offered with the roadster kit. Any ideas where I can get these covers? I see lots online, but I'm not really sure how to know if they will fit my rims.
Any suggestions would be greatly appreciated. Thanks

[Blitzboy54]

The hole is measured in MM. Just measure it and search center hub caps and however many MM's you have. Ebay is great for that stuff.