I had a local house and car leather restorer do a similar job on my car. He removed the clips down the offending side, peeled off the leather and added strips of foam on too of the worn sections. These were then glued in place.
This is a half arsed approach because I have heated seats, and the proper method of removing all the leather, and cutting/sculpting new foam pads would have destroyed the heaters which I didn't want.
This lash up was done last summer and is fine. The new foam is slightly too firm, but is getting more comfy with use. At £40 and 2 hours work it was a bargain. If the seat is well worn, try a breaker or flea bay. Full, good to perfect condition interiors pop up at £150 ish. Probably cheaper than getting one fixed long term.