No aftermarket seals/kits that I am aware of.
maxcichon replaced his with a non OEM top that has a double pocket for the window and a lifetime warranty.
Shoot him a PM and he'll give you the details, seems like he paid somewhere around $1,100

He and I did the replacement, we already had experience on that by doing the replacement on mine ( free - I was one of the lucky VIN numbers )

The DIY replacement is not too hard, but it IS a 2 person job. Only 'special' tool required is a $15 Harbor Freight pop rivet tool.
The SRT6 service manual provided in my SIG link has all the steps.
( you will need someplace where you can tie the open tonneau cover to something overhead to keep it open, any sort of prop device will get in the way )