I saw your seat suspension on the JD On-line parts site. Here's what I'd do:
1: If just the end broke off, soften it over a torch and wind a new pigtail on it.
2: If it broke in the middle, take the good spring out and hang it from a wall hook, fence post, loader bucket, don't matter.
Take a heavy object: cement block, iron weight, floor jack, etc. whatever it takes to stretch it about and inch or so.
Get over to Home Depot, Lowes, TSC, ACO, Farm & Fleet, whatever and find an equivalent spring based on the rate. This means for the length you need, get it to stretch the same amount. A good spring scale would certainly help in this deal.
If you can't find a 'pretty close' equivalent, make one up from a garage door spring chosen for which the rate is about the same for the length you need. These stores carry a full line of springs with rates and lengths suitable for all farming equipment. I even found one perfect for the tail pullout on my windmill, there. You can wind a pigtail on the end of it by softening the end where you cut it with a propane or other gas torch. Get it red hot and wind it with a pliers or vice grips.
I've had to do this quite a few times, so its second nature for me now.
Check the shock absorber out for leaks while you are at it. A bad damper could have put a heavier strain on the suspension causing the springs to be over strained.
Might want to cut back on the Big Macs until the seat suspension recovers from surgery....
