Just a few links to some framing options if you're having trouble finding one for the 18x24 Maps. This is just my personal opinion on some good options.
Has many options but here's a few I like: Option 1
& Option 2
. 2. Micheals
A bit of a cheaper option here. They sell big frames in 18x24 in Black, White, Grey Wood, and Walnut right in the framing section. Can't miss them.
3. Homesense If you're into digging and have patience, you might have some luck buying already framed art, removing the art and replacing it with a map.
4. Kid Icarus
If you're in Toronto, Kid Icarus
sells black and white minimal frames that are made exactly for these prints.
5. Rustic Works
If you're looking for something extra special and are in the Barrie Area get in touch with Keith at Rustic Works
for a custom Barnboard Frame. He's a busy guy so be prepared for lots of lead time.