special Propane mixer, help needed

[Terrick down Under]

G'day all. I have a 93 7.4 auto that runs duel fuel. Propane and pump gas. Down here the pump gas is expensive so I run the propane and have been very happy with it for the last 400000+ kilometres.
BUT, over the last month it has developed a couple of faults. Namely a flat spot just of idle and bogging down around 4000RPM, I have replaced the surrounding components except the mixer and the stepper motor. The only place I have found one of these mixers is the UK, and they have just emailed me to say they don't carry them anymore. I can't find any model or manufactures details on it anywhere.
My question is....does anyone in the USA know where I can get one of these.


TIA.