turn signal indicator wiring

[khall]

I have a cobra in my shop that has a properly working lighting system with the exception of the turn signal lindicator lamp (single Lucas) on the dash panel. The system uses dual bulbs in the rear and a two terminal thermal flasher. There are four wires hanging from the wiring harness under the dash panel. They are the two leads and associated grounds from both L & R side turn lamp circuits. I hope that there is a simple way to connect these to a single dash inicator lamp - perhaps using diodes to isolate each side? When both are connected to the indicator lamp it essentially creates a four way flasher when either left or right turn is selected. I assume that the original builder planned to install a hazard flasher using the unused wires in question, since the thermal flasher is hot with the key off. There is no hazard switch.
Any ideas will be appreciated.

Thanks