i have the butler creek caps on several of my scopes but they break all the time and i really truly hate them. on more than one occasion i've had to use a field improvised solution, and one thing that seems to work pretty well is simply carrying the rifle muzzle down so that rain doesn't get on the objective and taking a plastic water bottle and cutting it in half with your knife, then slipping the bottom half over the ocular lens housing. viola!
there are many products out there designed to cover and protect scopes and glass, but none of them ever worked well for me. they are always too heavy, or bulky, or slow to don and doff, etc. so some other things to try
sheet of saran wrap over the objective
ziploc or sammich bag and rubber band
one of your gloves over the ocular
also, i keep a can of compressed air in my vehicle which is a pretty good way of removing stuff from the lens but keep in mind it will cool it off and could cause condensation