More Poundland stuff for the cash-strapped. Not my photos; in the true spirit of free enterprise, there are people selling Poundland stuff on eBay for £3 to £4 +p&p. So I borrowed their photos.
Map case. Sold for bicycles but works fine if you're on foot too (you might want to add a bit of paracord as a leash / lanyard). Almost 28cm square, so large enough to display two panels of an OS map on each side of the case.
Belt pouch. Sold in the travel accessories section as a "passport holder", and it would make a fine one, but the pouch is gusseted and will expand to roughly 13x9x4cm; enough to swallow one of those posh roller-clasped survival kits. Also, there's a zippered front pocket under the flap where you could actually stash your passport, or some cash, or whatever.

Note that earlier models came with a neck cord as well as the belt loop, but later ones are belt loop only.