Can't beat $11 moroday adhesive mat for value if you don't mind cutting your own pattern. Closed cell eva foam, feels like a similar density to the tail pad maybe a bit firmer (called rubber in the description for some reason).
www.bunnings.com.au/moroday-400-x-500-x-6mm-adhesive-rubber-mat_p4000015Covered the top in masking tape & drew the cut lines. 3 discs on the rotary tool for a wider groove & taped a wooden spacer to the handle for depth, I cut a bit past halfway.
Going well on my surfboard so far. Hot glue on the front corners prevents spray around the rail peeling it up. Should've cut the grooves wider though. Comes in a 3mm thick 3m roll ($20) aswell, might try this thinner stuff on my foil board.
Cheers