Here in the Canadian North West we try to get colour photocopies of the original topo maps, then laminate that, leave a 1cm margin and carry that, leave the original at home on the wall!
If we have to carry a tonne of maps, then we go to the 1:500,000 Visual Navigation Charts, pilot's maps, which are printed double-sided, and have enough detail for river or bike trips.
Silicone map cases work well in cold weather as well as in hot weather, but yellow over time.
Vinyl map cases are brittle in the cold (-10C)+ may spontaneously absorb photocopy ink from photocopied maps, into the plastic under warm conditions, make the map case itself unreadable.
Hence the silicone map case...Orlieb makes good ones, but nothing beats a laminated map if you can afford to do that!
Print shops may let you pool together laminations such that many smaller items fill up the full width of the laminating plastic, and then let you cut up items on your own, for a lower price...