mom2acrew,
Pacific Cycle said that they have no replacement seat cover for us to buy for my Instep, which also happened to be discontinued by them.
I ended up unscrewing the seat cover (12 screws) and mending two tears. the left seat has a 7" tear and the right seat has a 3" tear.
the side with the 7" tear is my 43lb son's regular seat. the 3" tear is my 35lb son regular seat. both tears are at the seams near the centre "divider"
not sure when the first tear appear but the the 2nd tear appeared just after my DS2 reached 30lbs.
since the Instep was suppose to take 50lbs per seat, I was pretty disappointed that the seat cover tore at 30lbs.
its just wear and tear at the seams but wish Pacific Cycle has done double stitching for the seams of the seat cover.