Stop whinging, start printing. Do you not know a business opportunity when you see one?
On the other hand, maybe the lady doth protest too much.....
Pocket Mountains Central Highlands is 15x10.5
Cicerone's Walking on Dartmoor is 11.5x17
Discovery walking guides are 21x12
National trail guides are 13x21
They all fit into the pocket on my Paramo windproof smock, Montane Venture jacket, and Paramo Velez smock.
Personally I particularly like the Discovery one's as they are spiral bound and you can fold them right over and put them back in your pocket open at the relevant page.
If just on a day walk I tend to just photocopy the relevant bit and take that.