We own LensCoat rain covers in various sizes. We have used gallon or 2 gallon freezer Ziploc bags with success. These OP/TECH covers were also used with success https://www.amazon.c...pf_rd_i=3346261
Even back in the old days took a small plastic bag and put the camera in it and placed a rubber band on the end of the lens and cut the plastic end off for the lens to poke through.
Many different ways and cost.
Storing in your pack use a Ziploc bag and that will keep the unit dry if your pack takes a unexpected dunk in water.