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.
You can find fiberglass and the hardener at stores like home depot but if you are able to find a specialty store it will probably be cheaper to buy it in bulk so you have enough to make a few planters
Work outside and with gloves and a respirator. Make sure you read the directions on mixing the resin. Too much hardener and you wont have enough working time before everything starts to harden, too little hardener and it could take days to solidify.
Do yourself a favor and lay cardboard down over your working area, things will get messy. And also wear long sleeve shirts. Nothing sucks more than getting the resin on your arm.
My method is to first mix up some resin and to completely cover the pot in just resin then lay fiberglass sheets that are about 3" x 8" and brush more resin on. Too big of sheets and they will be hard to handle, especially once you start getting the resin on your gloves.... the fiberglass mat will want to stick to everything.
Once you have covered the planter in a layer I like to let it sit and harden before i start on the next layer. The amount of layers you put will depend on the size of the planter and whats going in it.
Our 18" x 18" x 2' high planter framed entirely out of cardboard i only used 2 layers of glass and i also brushed resin on the inside of the cardboard as well. Its solid. It does only have fake flowers in it but i'm certain it would contain a full load of dirt.
Once you have a few layers down i would suggest letting it harden over night and checking to see how strong it is. if you want it stronger just add another layer of fiberglass.
The finish does not need to be smooth or perfect by any means. Once you cover with the textured spray paint , those little discontinuities will make it look all the better.
If your looking to have a glass smooth exterior that will be harder to accomplish and i don't feel like covering that at the moment... sorry!
Use a drill to make a drainage hole in the bottom. If you are using fake plants i suggest to use some construction adhesive to glue a brick or two onto the bottom the keep it weighted down a bit more.
Once the pot is fully dry check over the whole thing. when fiber-glassing sometimes there are little bits of hardened mat sticking out. These are sharp!! and will cut you, Make sure you sand them down with some sandpaper.
To prep for painting i like to give the whole thing a quick sand anyways just to create a better surface to bond to.
Give the planter 2-3 light coats and let it sit over night.
Fill it with dirt, fill it with plants and enjoy.
The pot on the front page is actually made entirely out of cardboard and fiberglass, no wood framing.
I tried to get a picture to show the texture but it didn't turn out the greatest.