I've taken cheapo ~40 gal plastic lock boxes from Home Depot and added weatherproof stripping, from the Pelican website I think (just find a Pelican box of a similar size, then search for their replacement weatherstrip for that item - trim the end to fit). Check the box before you buy - it should have a rim on which to mount the weatherstripping, which so far every cheap box I've looked at has. You do not get all the strength and reliability of the Pelican (and weatherproofing is by no means warranted), but the box itself is reasonably weatherproof - and inexpensive.

Given that I only open / close my boxes every 3-6 months to pull or replace gear, this works great for me.