I have personally used the Jet Armor kit and was very happy with it. Sea-Doo Upholstery also makes a kit, and I will probably try them on my next project. The Jet Armor kit is only a 2 way stretch vinyl and requires lots of heat and stretching to get it looking good. I believe the Seadoo Upholstery kit uses a 4 way stretch vinyl, which is easier to work with. I have also purchased Allsport 4 way stretch from Rochford Supply to do a couple of bench seats and jet ski seats with great results
Here's a link to a thread using the Jet Armor kit
New upholstery - Challenger 1800