I've used SEM leather and plastic dye with great results. They also provide exact factory matches. I've even got old stereo parts that were dyed but not used that still look good after 10 years even though they live in the nut and bolt box which for me is a plastic tub 1.5 foot by 1.5 foot by 3 foot.
No idea on leather seat covers, but you might try checking with your local upholstery shop. Might wind up getting a set custom made with the exact material and design you want for about the same as a mass-produced set from China. And, plan on replacing both front and rear seat covers unless you just want to go back with exactly what you have now or it won't look right, whether you go with mail order or custom made.