Some recos for you ...
Aqueon Small Aquarium Combos | Products
I only had their 10 gallon version with hood, light, and filter.
Their filters (which you can buy alone), are excellent, and easy to "baffle" with a sponge
and rubber band (so the flow doesn't blow the betta around!).
Never had any issues with this brand, available at most pet shops....around $50-$80 bucks,
less without the light hood....you can make a hood for cheap.
But also look on Craigslist...lots of people sell aquarium stuff on there....just make sure
they let you test the tank for leaks! I fixed many cracks with water proof sealant though.
Another is the Marineland Eclipse 6 Gallon ... Yahoo! Shopping Search Results for marineland 6 gallon
Also easy to baffle the built in filter, they aren't glass though...but never scratched like some other
acrylic tanks I had.
Walmart sells a Hex 5G...they scratch super easy & the filter peeved me off.
For space...hmm....I'm looking at my desk now...I think a 10G would fit, but it might be a tight squeeze? Depends on how much room you need to work! :) A 10G will weight over 80lbs full...make sure your
desk can hold that! :)