I used this kit:
https://www.bettercarlighting.co.uk/ind ... ductId=753I fitted the push switch into the hole in the trim piece below the steering column where the ignition switch should be - (mines a Plus 2 with a Plus 2S 130 interior so the hole was going spare, and I used a pair of alloy plates to sandwich the switch in place). The switch is a neat flush fit and it is illuminated when the ignition is on so you can find it, and it flashes brightly when the flashers are hazarding!
Very easy to wire in, with good clear instructions. I connected it into the loom where the indicator lights split from the column switch to go fore and aft - I crimped bullet connectors onto the two feed lines and used four way connector blocks to add the extra wire on each circuit, and mounted the flasher unit behind the dash on a sticky pad. A bit fiddly and beware the paper tags on the wires which tell you where to connect them - mine fell off..... but it was easy to work out which was which by studying the supplied wiring diagram.