This is an alternative mounting method for the lights which can be found using the Amazon link below. This bracket is meant to be riveted in place and still allows the light to be removed for charging. I had 3/16" rivets on hand and the bracket is designed for use with such, however it would be simple enough to alter the diameter of the rivet hole to better suit your needs. Of course, you could use a nut and bolt if you have access to that part of your kayak.

I used a soldering iron to set a M5 x 5mm x 7mm threaded insert embedment nut into the top of the bracket and a M5 x 20mm hex socket head cap screw to keep everything together. I used these materials because I had them on hand, I have provided links to both items below.

I will be printing in ABS and will update with finished install pictures soon.

Lights:
https://www.amazon.com/Botepon-Operated-Navigation-Waterproof-Kayaking/dp/B09BZT5C1S/ref=sr_1_3?crid=20YEF58GEJHW0&keywords=usb+stern+light&qid=1685719230&sprefix=usb+stern+lig%2Caps%2C116&sr=8-3

Embedment Nut:
https://www.amazon.com/Knurled-Threaded-Embedment-Assortment-Projects-300PCS/dp/B08J6JG97C/ref=sr_1_10?crid=3EPTG6A5E7MQB&keywords=m5+x+5+x+7+embedment+nut&qid=1685720726&sprefix=m5+x+5+x+7+embedment+nut%2Caps%2C92&sr=8-10

Screw:
https://www.amazon.com/Comdox-500pcs-Button-Socket-Assortment/dp/B06XQMBDMX/ref=sr_1_4?keywords=comdox+500pcs+m3+m4+m5&qid=1685720862&sprefix=comdox+%2Caps%2C81&sr=8-4