There are a lot of aftermarket companies that offer seat covers that are leather. I looked at a set for my Miata. A good two-piece set that looked like factory with all of the seatback pouches and logo stitching cost around $600.00 for my Miata. Just do an internet search for "leather seat covers" and you will find lots of manufacturers. I don't know if they have a Solstice kit yet, that may take some time.
I am getting my seats done in leather by a company that does it for the dealer. The have quoted me a proce of around $1,200. for seats and stearing wheel. They will put it in my price of the car. I got in when there was a restriction on leather seats. I have the Sly so plan to do the seats with black on the outside and gray on the inside to match the car.