You can build your own in any shape an size for relatively cheap and with few materials.
What you need:
1" x 2" wood (to make frame) scour sites like Craig's list to get free scraps
cardboard or 1/8 plywood (depending on which route you take. will explain later)
textured spray paint
First step is to come up with the shape of the pot you want to make and its dimensions.
If you are putting in real plants with dirt i suggest using the plywood route but if you're just putting in fake plants as we did in some of ours you can get away with cardboard.
To make it able to withstand the elements just make sure you cover both sides of the cardboard with the resin to seal it.
Once you have the frame together, cover it in either cardboard or plywood.
In these photos i'm using cardboard, i used a staple gun to secure it to the wood frame
We have had one made out of cardboard outside for over 2 years an it still looks brand new. Holds up to the elements just fine.