Pretty simple. I still have the spur; the original mount was re-tapped and is functional, but the bolt does not tighten by hand and is a PITA. The other alternative is to find a wing-bolt with the correct threading, but the only piece that I have that seems to share the thread size is an old hi-hat clutch, so the chances of that seem slim.

BTW, I am aware of the current eBay auction for a complete set (both mounts and plates), but I don't want to clutter up my life with extra stuff.