I broke my last Butler Creek flip up cover yesterday. Never spending my hard earned on cheap plastic crap like that again.
Instead, I've dug out the old bikini scope covers that came with the scope and have put them back on. I've also tied a length of string around the scope and the rubber strings of the bikini covers. I now have a scope covers that won't break and will remove just as easily as the butler creeks and won't get lost either.
Alternatively, you could use a rubber band to hold them in place.