I designed an replacement insert for the retainer clips of the Shelby CSS wheel center caps. Using the insert will require cutting off any remaining retainer clips on the cap, if there are any left.
I've made working prototypes in ABS. The final procuct will be made in a stronger, more flexible nylon. The new piece has an interference fit to the original cap and can be epoxied and maybe riveted in place for added security.
This should be available for sale in the next few weeks.