I did mine a few years ago. I had to order online and from several vendors. My order included the vinyl both pleated and non pleated, matched cording, perforated mesh for the bottom and dry fast foam. In addition you will need a box of monel staples, not stainless. I had to get those online also. An electric or pneumatic stapler is needed. I also had an industrial sewing machine. Add some brass grommets and a lot of work ( My bolsters are curved around the back area). I made mine match the originals exactly.
I figure at that time, it cost me about 300-350 for materials. I had purchased a walking foot sewing machine used for another 450. It was a fairly laborious and challenging job and I would probably NOT do it again. My buddy had his bolsters redone for about 500 and they looked good.
Note that the OEM foam is not self draining and when you open the bolsters you will probably find mold. Grady wrapped the foam in plastic but that degrades and rips over time. The new foam (Dry Fast or something like that) I used does not hold water ( or contact cement for that mater
) but it is pretty expensive stuff.
If you want to know where I got my supplies, I will try to see if I still have the invoices.