Here's what I used, these for the helm seats...but in a different color scheme than shown here because it was about 5 years ago...
http://www.overtons.com/modperl/product ... rchID=4006and these for the rear bench (2 pontoon lounges put together) they come in a 36" width and that fit with a little work on the shelf on the coaming panel....
http://www.overtons.com/modperl/product ... rchID=4006They were cheaper at that time though and for the rear seat it might be cheaper to have it redone depending on labor prices in your area....