Alternative replacement cable for classic sturmy archer 3 speed shifter?
If I was on a budget I'd go for the combination of the following two products (I'm not affiliated with this particular webshop):

Elvedes: 6451-3M - derailleur cable, €1.15
TOM adjustment nipple Sturmey Archer - adjustment nipple, €1.25

It doesn't look as nice as the original, still remains functional.

For US customers:
Cable anchor - $4.25
The cable itself still needs to be found.