I have used a quite a bit of this for my builds. In all different forms. I have gotten it from Utrech art supplies.
Save On Discount Utrecht Chipboard, Brown, 29 x 46 in & More Chipboard at Utrecht
There are other places but I found them the most reasonable. I had bought a box of 20 to build a Boushh & Boba Fett amongst some other things & I still have quite a bit of it left. It is great to work with & I recommend using a wood glue. If you want to give it a hardened edge use some super glue.
If you have any other questions let me know.