Search on www.quiltshops.com - I've seen some listed. I think Over the Rainbow has it among other places.
The problem with panels is that they tend to be crooked. I think I spent more time cutting out the squares than I did the rest of the quilt. For someone who's a control freak, it would be frustrating I think. Luckily, I have changed a bit over time and don't worry so much about it like I used to. :)