Hey, it's only September. You have plenty of time...
You have few options, it seems.
1. Bite the bullet and pay retail for whatever you can find.
2. Find
already produced pieces and try to get a discount on a bulk buy at either the retail or wholesale level. Businesses like getting rid of existing inventory - especially if they're overstocked and it's not moving.
3. Make your own using sheet plastic/putty, then casting them yourself.
Good luck with the project.
Glen