Lucas Switch Assembly

Hi
Having just joined the forum I'd first like to say hello and next ask for some guidance :0)
I've just taken on my aging fathers Triumph TR7T which has been well looked after but unused for the past 25 years. The last time he used it on the road was in the early 90's but always preferred 50's and 60's Triumphs. He is now sadly too old to ride anymore.

Anyway - I want to get the TR7T back on the road and am close to getting it ready for an MOT test. One are that I'd like some advice on is the handlebar LH switch assembly. I noticed the indicators weren't working and when I opened the switch assembly the innards were pretty much missing. The left-right switch is there but the entire rocker mechanism (which I think contained a ball bearing a some springs) has gone. I suspect that the switch was causing issue when my father was last using it and he perhaps got as far as removing the mechanism to clean\repair and never completed the job. I can assume this piece has long since been lost.

So, what would be my best options? I'd like to retain the authenticity but I don't think it's possible to replace just the missing internals is it?
The unit itself is a Lucas 187SA-L (black in colour) and I have found perhaps a couple of after market options here:
https://www.tri-corengland.com/acatalog/T140E-and-NORTON-LH-Switch-Gear-SPX008.html#SID=130
and
https://www.ebay.co.uk/itm/Triumph-...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Is either one a preferred option? I don't think genuine items are often available second hand but I could perhaps get a really cheap universal option just to get me an MOT pass whilst I wait for a genuine used item to appear on ebay perhaps?
Any Iinks to suitable options would be greatly appreciated

thanks in advance
Jon