Need a new cadense sensor

While out for a very windy ride over the weekend I realised I had lost my cadense sensor magnet connected to the crank arm.
I was looking into buying one from Ebay then did some digging and there is a suggestions from the states to use stronger magnets such as neodymium, however these conversations are nearly 5 years old and all the links on there are out of date.

https://forums.garmin.com/showthread.php?11854-Using-a-rare-earth-%28neodymium%29-magnet-to-replace-the-GSC-10-crank-arm-magnet

Looked at an online store in the UK who sells magnets but it doesn’t looks like they stock the correct size (something like 12.7mm outside diameter x 6.4mm inside diameter x 3.2mm thick) to attach to the peddle bolt as I was thinking of getting some with a hole so I can if needed use an allen key to take the peddles of as these magnets are supposed to be really strong.

Has anyone tried these magnets and recommend a stockist or someone recommend an alternative.