You can make your own heating system. But, keep in mind that you will need to get some 1 ohm, wire wound resistors capable of around 300 watts of thermal heat. Then you can wire 2 of them in parallel with each other and run them off of a 30 amp relay. This will give you about 600 watts of heat while the relay is engaged. The big trick will be putting in a safety circuit to shut the resistors off should they get too hot and also a timing circuit to shut them off after say 5 minutes (the motor is capable of handling the heat load). Also keep in mind that those resistors are going to get very warm. So, you will need to place them in the center of the vent duct, held in place by ceramic spacers and not allowing the bolts to come in contact with the resistors. Else, you are going to melt your duct, the resistor is going to fall down and really make a mess.