Easy and cheap (that's my style) fix is to hook up a $3 Radio Shack Piezo beeper to the turn signal flasher 'idiot light' in the headlight. It will beep every time the light flashes.
I did this after reading one of your posts on the subject and will admit it helped alot and as you say was $3. However I got all kinds of looks at stoplights (mainly from pedestrians) I think they were worried I was going to back over them.
I ended up removing it and force myself into remembering to hit the button after a turn.
I may opt for some kind of cancel device as driving with the blinker on is a recipe for disaster.