I wouldn't get anything else for their current bowls.
You can get a five gallon tank and divide it in two--each fish would have 2.5 gallons. That would be a little cheaper than a 10 gallon divided, but not by much. You could go to a pet store and see if they have any "critter keepers." They might be in the reptile section, you'll just have to look around. These are fairly inexpensive. You can usually find a 2.5 gallon one. I'd say they are probably a few bucks here in the US. But they are cheaper than getting a real aquarium, and they come with lids already so you don't have to worry about jumping fish.