I replaced the "decal" portion of the center cap that came with my Avant Garde M310 wheels with some that I picked up off of
eBay. The "decals" are actually a domed piece of aluminum with adhesive on the back and what I think is an epoxy (or some thick glossy coating) covered decal on the front. They look the same as OEMs. The center caps for my wheels were 68mm, I suspect yours are as well.
I used a hairdryer to heat the adhesive a little before using a small screwdriver to get under the edge and start prying up the stock decal. It worked out well, and I only had a little mark on the edge of the cap where I started prying, which really isn't noticeable. Pix below: