Good Arduino motor drivers
We don't really answer "shopping questions".
You could contact several suppliers like Adafruit, sparkfun or maybe even Digikey, Farnell etc (ebay?).

If you search for: "15A dual h-bridge" you will find some motor drivers which should work for you.

If a driver can control a dc motor in 2 directions can it control 2 dc motors in one direction each?

Where are you going to use them for?
If you're only going in one direction, you won't need a motor driver.

An MOSFET (per motor) is good enough if you only drive one direction.
If you want both motors to be able to turn each direction, a dual h-bridge will do.