Check with a locksmith. They can make a key using your original locks. but beware, some of them are pretty expensive. You can probably take one of the side panel locks off and take it to the shop and they might be fairly reasonable.
If you still have the original key, you can take it to Home Depot and have them cut a copy on a Ford 24R Blank. It will be longer, not a problem, and thicker, a bit of a problem. You need to hit it with a belt sander to thin it up a bit, but they work fine, Yamaha also has a blank that will work if you can find a dealer that sells them.
Bare
Bare