IMHO, not difficult to make. Our boat came with a total of four. Two long ones for each side & one in front and another in the back.I am terribly afraid that the CO does not even have any wedges.
They had been carved or ground from some pieces of teak, but I thought there should more uniform support around the whole spar circumference.
I used some scrap hardwood, about one inch square or less. Epoxied some quarter inch X about 2" thick wood onto one side to create a sort of a long "L" shaped piece. I cut it into pieces about an inch or less wide. The longer side had to be sanded down and shaped some to fit in the slot by the spar.
They all dropped into the slot all the way around, snugly. I put a bead of sealant around the top part to hold them in place. Then replaced the vinyl cover over all to keep water out. Then, lastly, put a sunbrella cover over all of this to protect the vinyl.
I wish I had some photos of the process. It's not difficult to do but the describing seems to take too many words.... !