The foam and straps from a seat which hasn't had much use will put quite a bit of life back into a well used seat.
Obviously it won't do anything for the fabric, unless you're lucky enough to find the same pattern, and swap the cover too.
I'd expect it to be a reasonably cheap option.
Don't forget to experiment with the donor seat first: you need quite strong fingers to re-attach the clips.
I have dismantled a seat with a broken frame (to save the non-metal parts) and did use that webbing/straps on the seats from an old CL.
One day I may get the enthusiasm to change the foam..