left hand switch block (indicators and horn)

enclosed is a photo from the switch in question.

showing this micro spring and slider cup i was talking about.

i have enclosed in this pic, the end of a normal everyday biro pen
and its spring to show the difference in scale between the two....

yep, and they're actually quite high-rate springs due to their short travel.

If you can't find a listing for that size and guage of spring from new, I'd say it's gotta be either;

1)Rob from another switch unit, if you can find similar, or;
2)Make your own spring, from piano-wire wound around a slightly undersized pin/rod.
Measure the springs' guage with a vernier, source the wire from hobby/model shops.
Experiment with length / spacing. It won't have to look perfect as long as the plastic plunger acheives it's 2mm or so of travel at a similar spring rate to it's pair.
3)Where (along it's length) is the old one broken? May be possible (if broken near the end) to stretch the spring to it's original length (compare to the other) and test if it's able to give similar movement / rate.

Looking at that spring, if you know any car/truck mechanic's maybe they have an old auto switch or turn signal switch laying around that might have a similar type spring in it you can adapt?

I'll agree with RChaloner and Stocktoy. It may be easier for you at this point to rob a spring from another switch. Those tiny springs are very common to keyed automotive ignition switched with detent balls to hold the switch in various positions. Failing that, I would send off your broken spring to a spring manufacturer and have them size it up for replacement. It's a simple compression spring.

the problem is that im also up for another one of those slider cups....

the most sensible solution here is to locate a left hand switch that
can be parted.....not easy i suspect.

or

find something of a left hand switch block from another model that will
somewhat fit as suggested by RChaloner......................arghhh

why couldnt i be normal and like new bikes....?

It's all 'swings and roundabouts' ...

My '79 switches took less than an hour to strip and clean, no problems.

But fabbing and welding all the missing seat / rear light brackets and frame rails back onto my frame took bloody weeks (admittedly somewhat part-timely) !

Seriously though, if alternate switch assemblies are tricky to find, what's to loose by having a go at making your own, namely;

1)measure OD of the other plunger and buy some black nylon / delrin rod - you can profile the roundend in a drill chuck with a file, and drill the spring recess with correctly sized drill bit.
2)Do the spring wire sizing thing and get piano wire of that size, the main trick to winding it is to start with a smaller (than required) bar for the inner diameter, as the spring 'unwinds' a bit once released.
Just wind the spring wire around the former tightly by hand (finger pressure is fine for that size) with all coils closed together, then stretch it out to the required coil spacing.
You'll have to experiment a few times with the ID to get it right, but the whole material costs for this 'experiment' is next-to-nothing, will only take an hour or two and you never know, you could get it right first time : )