Keep your eye out on eBay. I lost one of mine about two months ago on the lake. I placed an ad on craigslist stating I lost it. I thought it was gone forever. Low and behold 2 weeks ago, I received an email that someone had my cushion. So I was able to get mine back.
Your best bet is eBay and craiglook. The same print is not available, and the apparent re-upholstering process is a PITA. It is a glue, heat, and stretch technique. PM me for a couple of leads I have on some replacement pieces.