has a ton of sheets in every shape, size and color. I recently ordered some for my son and they are fantastic and durable! They get new stuff all the time so keep checking!!
Also, if you buy the membership, you see new things before the general public and shiping is just $2.95. Usually shipping is $7.95 and the membership is $9.95. Since it is my favorite site and I order often, I bought the membership and it has more than paid for itself.
Good luck finding the horsey sheets!