Here's a list of the suppliers I've used and can recommend:
- Roarockit: https://www.roarockit.com/ - veneer (SFI certified at time of writing), foam, vacuum bags, and anything else you may need for making custom boards
- Marwood: https://www.marwoodveneer.com/ - veneer (FSC certified at time of writing)
- Home Depot: best price for Titebond III I've seen, of course other tools and materials, and you can try the foam insulation - typically, the higher R value, the denser and stronger the foam is, but I haven't found any that match up to Roarockit's. The foam is good for builds where you may not need much precision, since it will deform a bit more under vacuum. I used to for my 55" longboard mold: https://youtu.be/qehf_n0B_rc
I'll try to update this as I find more that I recommend - please post your suggestions, too!