Well I had mine out a month ago, not to interested in pulling a pontoon again to get spring measurement, however I could, but not until summer. If anyone has one out of their machine, if you could get the ID, OD, wire diameter, # of coils, end ground or not (should be ground), free length, and assume they are spring steel you should be able to find something very close to original. With this information you can look at a company like Century Spring, enter these parameters and pick a spring that is exact or close. There are other spring manufacturers out there that may also work.
See if you can find someone with a spring that is already out and get these parameters, if you have no luck I will pull a pontoon and the springs later this spring/summer and get the info for you. However I will require payment of one ride in the Gobbler.
Just read your post again, you say you need almost a full set of springs, do you have one still? If so send me the info above and I will see what I can find for you.