Has Anyone got a solution/suggestion to this problem?
Indicators on my outfit are rather fast (I think barely legal) because the LED/Canbus equipped bike has a chair attached with victorian technology lamps. The fitting from Watsonian simply disconnects the left hand Bike indicators and wires in the chair lights.These being a front Side light and indicator and a rear stop/side/indicator. This upsets the bike system because the LEDs it is expecting are replaced with old fashioned bulbs. the usual solutions are the other way around i.e when uprating a vehicle designed for auto bulbs to LEDs. one suggested solution is to increase the wattage on the chairs lamps. 21 watt lamps appear to be the highest wattage available for these fittings , so I tried this but it made no difference. I have thought of reconnecting the left hand indicators on the bike, leaving the chair lights connected, to see what would happen, but this would require some way of masking off the bike indicators so the are not visible, and not sure if this would work any way. It must be a common problem for modern bikes with chairs attached.
(And Yes - I know that one solution is to take the chair off and ride it like a proper bike with two wheels, so don’t bother suggesting that , its not going to happen!)
Have you tried using the exciter coil of an auto motive relay and running the chair light off the out put side. The relay existed coil may perform similar to both near side LED indicators.
Bloody electronics! 
What bike is it?
You might try changing the chair bulbs to equiv. LED replacements?
Its a Cali 1400 touring on a 16 Plate
I suggested fitting LEDs to the chair to Watsonian who Fitted the Sidecar to the bike . They say that does not work (they did not offer a reason) but said that if it was then they would have fitted LEds to the chair in the first place . Also I have not been able to source any LED type lamps with the fittings required (one is a Bayonet type and one is a Festoon type )
AS to the exciter coil solution from Mike H , I guess you mean just using the coil terminals from a “relay” and wring these in serious with the flasher one on the chair?? Not quire sure what the exciter coil would do , if that what you meant.
I think I have to find a way of fooling the trigger pulse from the CANBUS Controller on the bike into thinking it is operating the original LEDS on the Bike
I can see no reason why LED chair bulbs would not work. You should be able to add them to the circuit with no problems. If you are looking for bulbs see: http://www.dynamoregulatorconversions.com/
They come highly recommend, not as cheap as eBay but quality is excellent. They are happy to advise on fitting etc.
Steve.
Going by my recent Google searches (for other reasons) there seem to be LED replacements for filament bulbs in all the common socket styles, even festoon.