I agree with other that you probably don't need locking nuts.
Try this one if you really want them https://www.johncraddockltd.co.uk/kbm100450-locking-nut-for-wheels-56-code-a.html
A 2nd hand set of 5 wheel nuts for an ally wheeled FL1 on ebay = almost £20
Similar price for the correct key, and with no struggling to get the old nuts off.
Also a slight deterrent, not just for the wheels but also for my matching, almost new tyres.
Thanks for the link. I've now ordered.