The OP asked about single use motors. If that is what you are looking for, you are limited to Estes, Klima and Aerotech. Aerotech is supposed to be releasing a line of single use 18 mm composite motors under the Quest brand, but they are hung up with production and certification issues. Those are the only options for single use motors.
Like many of the others on this thread, I'm a fan of Loki 38 mm loads. But you are limited to 38, 54 or 76 mm sizes, and while assembly is not as hard as most perceive, it is far from the simplicity of single use. It should also be noted that many 29 and 38 mm Aerotech reloads also ship without hazmat. They are currently trying to certify the first hazmat-free J motor. The closest one can get to single use is CTI, but be sure to find a local source for them, or else the hazmat shipping will eat into your rocket budget.