In The States, I've used an outfit called GeoPrinter for one-off maps/charts. They'll do heavy synthetic-paper and laminated-surface prints in large sizes (up to about 10 feet square!) They have a handy little program that lets you design from various sources and upload the file to their site -- they then mail you the resulting print from North Carolina. Sorry, their primary business is for classrooms or mounted displays, which is not exactly what you're looking for. But the prints can easily be folded and are pretty durable. You might have to make do with inch-pattern rather than metric. They do have a price list online, but I don't have the bookmark handy.
For personal use, I just find a local shop with a big ink-jet printer: a blueprint service, or sometimes Kinkos. Standard paper size is 42 inches wide by just about any length. If you use uncoated paper, you can make hand notes. (When I'm done, my charts look like a thousand monkeys doodled on them!) I find annotated charts extremely useful for navigating and records -- and I suppose they make interesting keepsakes -- but ultimately I consider them disposable. You do have to protect uncoated charts from getting wet. I roll them (rather than fold) and store them in a plastic tube bought for the purpose at a marine supplier.
Luangwa? I'm afraid if you're looking for a print shop in Zambia, you're on your own
