I bought a home laminator which was on offer from W.H.Smith for less than £10.00 a couple of years ago It did the job but it worked out to be more expensive than using Toughprint waterproof paper. Also, the lamination made the map stiff and awkward to handle.
I find that if I print maps on standard paper and keep them in a stout plastic bag that they rarely get wet. But then, unlike some walkers, I don't normally annotate my maps with marker pens.
When backpacking, which makes if more difficult to keep maps dry, I use Toughprint paper and print on both sides of each sheet. This reduces the cost per A4 map to about 25p.
Another solution is to paint the map with a clear varnish from a hardware store (much cheaper than buying from a stationers). I imagine that you would be able to annotate it with a suitable marker pen. The map tends to yellow in time. Hmm... on second thoughts it might not work because the print would probably run. I used to paint the original, not copies i.e. before the era of home printers.
Hugh
I grow old...I grow old...I shall wear the bottom of my trousers rolled. T.S.Eliot.