The original Lucas dipswitches now command huge sums on ebay. In 2014 Tony Betts produced a finely crafted and very reasonably priced replica with the correct long body (still available).
If you want to make something yourself, the shorter £20 Lucas 31482 ‘short’ body is adaptable with a bit of fiddling. It felt better to use the original than the cheaper repro switches available online, just for the potential quality/longevity of the switching mechanism, as well as the visual link to the original item.
The plastic handlebar 1″ diameter mount needs carefully grinding out on either edge to suit the larger diameter of the Austin 7 steering column, and the existing metal strap can be re-bent to its maximum possible extent, and two new holes drilled through it to allow the screw to pass through the barrel retainers and allow tightening up.
It is tight, but works, just! It is also less bulky than the original; I’ve got mine set vertically on the column just ahead of the starter knob so it doesn’t obstruct anything, and has the main beam setting pointing directly towards the driver.
The electricial fittings are suitably weighty and require the wires to be soldered in. Many appear to be using this quite happily as the dividing switch between (modernised) dip and main, rather than as a trigger switch for a relay.
I am using heavy duty black pvc cable with the three wires supplying the headlight feed and taking back either main or dip (which then meet with a junction box on the loom, joining the two pairs for each headlight). In order to prevent potential shorting in the small space available below the contacts and metal column below, I’ve used a rubber padding membrane between the Lucas unit and the column on which it is tensioned down onto.
So, its not perfect, but it’s a cute switch which you can alter with not too much effort.