Hi,

Could be a dangerous game. I know a Frenchie with another TX-brand that fried his transmitter and the mains-fuse while connecting the following :

mains--> 12 volt power supply --> charger --> TX --> interface --> PC

Just know that when your TX is in use for pc-sim (and that the RF-part is not in use, either by removing the RF-module, either by removing the cristal) the TX only uses about 30mAh instead of about 240mAh (depending on your TX). That's 1/8 of normal consumption.
You could try anyway with a 9volt-AC/DC adapter, but I would'nt dare.

Olivier