Make your own. I just made one using West Epoxy and some craft felt. I built a 3 sided form (2 side and a bittom) lined it with wax paper, place a piece of felt, painted/brushed mixed epoxy on it and repeated then folded the wax paper over and put a piece of wood on top and clamped tight. After it hardened I removed and trimmed. I'll post some photos tonight. Youtube is your friend.
