Unfortunately, being an Agricultural engineer and welding Narrow Boats for a living, I can't think of a single application in my world where those springs are used apart from rat traps. :-
Interestingly, I had a look at all my knockdown targets yesterday (brand new Gamos) and only one has the reset Spring --- so are they really necessary to operate ?
Edit :- the springs you need are called torsion springs.
All the best Mick