I am pretty sure deep cove outdoors sells them. They used to sell blocks that had adhesive on one side. You can save on postage and combine the shopping with a paddle from deep cove 🙂
Delta kayaks sell thigh braces that should fit most boats
If you are looking for padding, I presume you are learning to roll. Let me know if you are heading towards deep cove and would like some company. I paddle every Sunday. At the moment not far because I am having issues with my shoulder, but rolling practice is always an option.