Yes. It won’t work.
This might though:
I sugrued a magnet to a light and put a pair of similar magnets inside and outside the bag. Take the light off and the pair of magnets stay in place on the bag. A bit of a bodge but it works well. I got the magnets online from Emagnets.
Do you use a support for the Carradice ( a bagman?) If yes you could use this which allows you to fix the light to the support.