691656 Starter Solenoid
This can be used to replace a double pole solenoid with the following wiring modification.

Of the two small activation leads fitted to a double pole solenoid, one will have 12v when activated the other will be an earth.
Once the earth lead has been positively identified, it can be isolated using insulation tape as this is not required.
The single pole solenoid is earthed via its metal mounting plate.
The 12v activation wire is connected to the single spade connector on the solenoid.