the actual lamp supplied in the WASP tail-chop is an absolute piece of 5-cent junk. (No offense to WASP who is one of the best contributors to our bikes).
I went through 5 of them (thanks to WASP's great customer service) before I got tired of taking it apart altered it for something else.
I used a custom chrome lamp with bulb (since the LED ones are too $$ and burn about once a year) for about $30, but due to its larger size I had to saw off the plate bracket and create another metal piece to bolt onto to the main bracket in order to fit the light.
There are smaller lamps that might fit and only require to drill a couple of holes for proper fitments. Check out custom Chrome, or
Dime City Cycles - Vintage Cafe Racer & Bobber Parts; Delivered Anywhere in the World!, they seem to have cool lights.