If money is no object than I would go with Corbin,"kind of pricey but you get life time warranty" any complaints they will fix it for you to the way you want it. Very customer orientated and motorcycle friendly people, I went to their main plant in Hollister and everyone was friendly, from the person that was sweeping the floor to the secretary, to the guy that built my seat to the shipping clerk that refunded my shipping cost since I had ordered it with shipping but they had my seat ready to go out and since I was at the Honda dealer picking up my daughter's Grom I decided to stop by Corbin and see how my seat was coming along and they said it is in shipping and ready to go out and if I wanted it they would take it back from shipping and give it to me. There were other motorcycle guys there to get their custom Harley seat made and was waiting in the customer waiting room and they went outside to take a smoke break and noticed the Grom in my truck and went over to look at it and started taking pictures of it. Price range for Corbin is average $300 custom made depending on material used. Mind was snake skin design on leather and tanned to the color scheme of the paint job I was going to use on my Grom.
For cost savings I would go with the seat kit that has a ready made cover and preform foam that you have to remove your cover and cut out your seat foam and glue this pre-form foam in and stable the seat cover to your Grom pan seat plastic. I think the price on that seat was around $125. Not sure what company that made this seat kit but if I see it posted I will up date this post with the link.