New old stock, original CEV 218 / 04931 Amber reflector for early Tomos forks.
1978-1991 Tomos commonly had these.
94mm long by 27mm wide. Reflector is 6.5mm thick not including the mount. Mounting hole is 8.5mm in diameter.
Derbi Variants also had a similar CEV reflector but with 12mm diameter mounting hole. Perhaps you can just enlarge this hole?
These of course can work on any bike you want to try and mount them to. There is about 18mm of standoff from the back of the reflector to the center of the mounting hole.