Aquatic Transformation

[Surrealasm]

So for the last 4 or 5 months I've kept my two FBT in a smallish tank. I think it's about 2.5 gallons, but I'm not really sure because it's shaped strangely.
For the entierety of this time I've had about a 60/40--land/water mix going, and they seem to be getting along great. They chirp and hump and all that good stuff.
Recently I've been wanting to upgrade their enclosure-- they seem to spend about equal time on land and water, but I love watching them swim.
Thus I want to move them to a 5 or 10 gallon tank that I have, and do 25/75 land water.

I've been trying to find water pumps to suit my needs, however, maybe because of my own inexperience, I can't seem to find anything at all that's appropriate.
Could y'all please give me some good recommendations/ideas on what to look for?