I think I just found the solution. I have a 98 3200SCR and that clip has broken several times. I bought 5 or 6 last time (several years ago) and have two left, so started looking for a solution. Found these at West Marine (but you can find them cheaper all over the internet):
They are http://www.westmarine.com/webapp/wcs...9#.UpIxCcSsi-0
the 3/8 is the same diameter as the loop on the seat, they are soft so can open and close to receive the seat but hard enough to keep a hold of it (I hope! Time will tell) and I figure a pair in the place of each bracket (so 4 in all) should give the strength we need.