Just wanted to share this with anyone in the St. Louis area. I am 6'3" and have an issue with the non adjustable seat in my Prius. I recently took care of that issue and wanted to let you know there is a fix. I went to a place called Dr. Vinyl located in St. Peters, MO. They replaced my seat with the seat of a 2008 Corolla that had the adjustable seat option on it. They did have to make some modifications to it by using some pieces of my original seat, but the bottom line is, I have an adjustable seat and I am thrilled.
I think that's what another member here (cycledrum) also ended up doing. One question. Do you find that when the seat is set to it's lowest position that it feels like you also get more leg room? That's how it feels for me anyway.