New subject, so hopefully I won't earn a vacation for double-posting.
I just found an interesting source for springs:
That's an 18" spring with the following specs:
3-3/8" coil length
3/4" coil diameter
1/16" wire diameter
(so that's a 5/8" inner diameter, if I understand 'coil diameter' correctly. I know my spare piece of 17/32" brass slides snugly down the center.)
Above it is the packaging from Schuck's / Kragen's. Part number 29004, $6. It's a 4 pack of springs, but only this one is useful. The packaging says "Pedal Return Spring Assortment."
Immediately below it is a Home Depot spring that sounds a lot like a "Ace #49", but I don't have the Ace to compare it with. It's 4 coils too long for a Nitefinder but otherwise fits fine. It has about 20# working load. The Home Depot part number is 684-838.
That's not the point - the point is that it looks a lot like the bottom-most spring when you buy it. It's tension spring, not a compression spring. Wrap the long end around something sturdy (such as the handle of a boltcutter you'll be glad you have to cut the spring down to size) and pull the other end with a pair of pliers until it gets to the right length.
Yes, you can pull it longer, but this is the coil distance it restores to after you compress it back down to its original length and let it expand back.
I remember someone saying their hardware store (in Malaysia, I believe) had no stock in springs. Here's an alternate supply. Is it as good as a factory spring? Nope. If nothing else, the ends aren't 'finished' into a pair or trio of compact coils neatly stacked. I'm sure stretching a torsion spring does it no favours. However, for someone who is otherwise bereft of springs, this could be an option, and a cheaper one at that. (The HD springs come 2 to a $4 pack, so you get 2" per dollar. This gave me 18" for $6, so you get 3" per dollar.)
It seems about as strong as the HD spring. I don't have a means to measure it, otherwise I could say for sure.
Fugly is a feature.