Get a large clear plastic kids lunchbox or storage crate.

Cut part of the front off and gaffa tape on a piece of clear aceate - the type used when photo copying overheads for the old style office projectors - easy to replace when it gets scratched. 

If your camera has a cable control - many don't seem to now :( use that.
Cut a hole in the back for your hand and tape a plastic carrier bag over that - like a old style camera. 

Gaffa tape box to tripod or use a gorrila grip punched through the base and mount that to your tripod head. On some tripods they have removable heads and the screws can be replaced - I've lost loads of these - hardware stores often have similar or longer sizes.

Throw in a few silca gels bags as mositure will build up inside and could cause fogging.  

I've used a simlar setup years ago when shooting on a beach where sand is a real PITA

Downsides:  Onboard Flash will be very diffused and maybe bounce back - use some cheap white card from an art shop for use as reflectors if it gets wet - throw it in a recycler.
 
You'll look like a complete idiot :) But at a wedding kids will love it - stick a toy bird on the box.

Pinky - you left the lens cap of your mind on again.