I pick mine up on ebay, flea markets, etc. You can also look online at drsfostersmith.com etc.

I just bought a big (11" x 13") clear glass jar with decorative lid at Target for $14.99

Target also has a very pretty egg glass vase that shows off the plants and gives adequate surface area for three low growing plants around a larger upright plant..plus rocks and driftwood (Pottery Barn...and I looked everywhere else for it)

I looked around the house and found a few things...Fishbowls, and I even found a large candle container, which I'm using for moss..

Thrift stores are also a great source for containers.

I'm with salvage_queen. I have a Goodwill about 2 miles from my house and all their price tags are in 1 of 4 or 5 different colors. Each week, 1 color if 50% off. And on the following Sun. & Mon, anything in that color that is still on the shelves drops to $1.29 ! I've been shopping for terrarium containers there & got some great stuff for cheap. I almost regret it is so close to home - I'm becoming addicted and constantly have to talk myself out of stuff!

I've started collecting Gesneriads, especially those small enough for terrariums. Before long, I hope to have micro-mini Sinningias to swap for other terrarium plants.

I believe Terrain carries a container similar to the one you are describing but the dimensions are 12 x 12 x 4 (so maybe a little thinner). The Terrarium Shoppe also carries some good terrarium containers.

I recently got one from an online store. Check them out. They have really neat glass terrariums.

Here is a link that might be useful: HPotter Terrariums