The only place that I know of offhand is Carolina Biological Supply. Check the link below. Keep in mind that the package offerred is for a 10 gallon sized aquarium.
also note this item cannot be shipped to the Pacific coast states nor Arizona and Nevada due to quarantinee laws.

Here is a link that might be useful: Carolina Biological Supply

I, personally, would love to see a pic of you new acquistion! Can you post a pic?

Never seen kits myself. You may have to simply do some research on terrs in general &, after figuring out what you like, go from there. There's lots of info on this forum though it will require lots of reading on your part. :) There are also pics of finished terrs in the Gallery as well on this forum that may inspire you.

With such a small terr, I think your biggest challenge will be finding small growing plants. There are some ultra mini (micro mini) african violets, from what I understand, that should stay quite small. Mosses will likely do well. [**NOTE: I do not advise using wild collected mosses -- depending on you zone, some require a cold dormancy. Also using wild collected is an easy way to introduce unwanted "critters" to you terr.] There are places that do sell mosses and other mini plants online. Here are links to 2:

Try Rob from Little Frog Farms. If he asks how you heard about him, tell him Paul from OB sent ya .
Little FrogFarms

Or Black Jungle
Black Jungle

Rob is a small independent and I always try to support the little guy. Blackjungle has a bigger variety. There are other terr suppliers too but these are the first 2 who came to mind. Oh and for micro miniAVs try places like Rob's Violets [no relation to Rob of Little FRog Farms]

For "decor" I'm not sure where you might look other than craft stores but if you are a 'crafty' person you might be able to make items yourself.

Keep us posted!
:)

You may want to think carefully about where you buy plants. From what I have heard from other people on this forum, Black Jungle is NOT good at getting live plants to you (dead plants and/or mislabeled plants, yes, but not live plants that you ordered). For other terrarium supplies I think they are OK, but not for plants.
-Jmcat

Terrarium plants?
When it comes down to it there are no such critters!
There are only plants, mostly of tropical origin that do best in warm humid situations which may be replicated in the confines of an enclosure.

For your small set up use what you can find locally at first until you get your feet thoroughly drenched and become interested in tackling a much larger set-up. to start use African Violet potting soil.
For plants a couple of easy ones are Selaginella kraussiana for a green mossy type ground covering and a Fittonia species (believe there are 4). These are easy and do spread but have great color
Fitonia images
with possibly a small Snake plant,
Snake plants images
This would be a great start, perhaps adding a small piece of a branch or a stone for contrast.

Thank you all for your great advice! I'll certainly need it as I attempt something totally new and outside my realm of expertise. It was great to get replies - I was worried I wouldn't hear from anyone! Thanks again!!