Now, how long before someone mentions those rubber rings from Grolsch bottle caps? 
:lol:
Not me, hate the stuff... but I do use these lawn-mower blades, or similar (I wouldn't want these particular ones, my current supply is black)(Although these green ones might suit Toe-Kee's swirly partscaster? :lol:):
http://www.islandworkshopsupplies.co.uk/product.php/site/froogle/sn/ALMQT028Just cut the blade bit off. Enough for 10 sets of straplocks in a pack, approx £3.50. Never failed me yet... (the Schallers have done, many years ago, when I was gigging - and I found they made "clonking noises" that came through on guitar parts).
My nephew asked for the Dunlop things for Christmas (in a guitar support package that included straps, tuner, etc, etc... he wasn't quite as economical as that sounds!). When I found the Dunlop ones, I nearly got him a packet of ALM mower blades instead. I thought that might seem a bit naff, though. However, after the event, he reckoned I should have done :lol: (he might even have got some himself by now...)