We don't currently offer a generator for hats, but we hope to have one available in the near future!
The Cap Builder is also an excellent online mockup generator you can use to create your mockups for different caps and beanies. It won't have the exact models we offer, but it's a tool you can use to demonstrate placement for your print files.
If you're wondering how to sync hat products to your store, check out this video. You'll need to first create a new hat product in your store, then manually sync it to the right product and print file in Printful (Stores > Sync > Edit).