I will be replacing my leather probably in the next couple of months and have been looking at a couple of places online that you can buy the leather. I am not planning on having a shop do this as the work is not too difficult.
Katzkin has a great reputation and their leather is used by a ton of car dealerships that swap out cloth for leather when someone buys a new car. The quality is at a minimum equal to OEM specs and usually a higher grade leather.
I also looked at theseatshop.com as they have some leather replacement options also.
I am not sure which one to go with at this point but I am leaning more toward katzkin based on price. I priced out replacing both bucket seats in the front and the 60/40 bench in the rear and it was $798.00 online.
I would be interested to hear which way others have gone with replacing the leather.