The pawl spring isn't a spring as such, in that it doesn't 'spring' anywhere. It is just a hook that acts to elevate or keep the sear elevated into the path of the breech block. And it does this by being tensioned by the trigger spring. So any suitable wire will do! You could start by simply annealing a clothes peg spring. No need to harden and temper afterwards - as it's not a spring!
Well after you have tempered it to red heat and allowed it to cool naturally, just unwind it until it's not too wide! Necessity is the mother of invention and all that........... But the basics of what you want are there.
Philb........ You REALLY are making a mountain out of a molehill. You are looking for something that is simplicity itself to make. It is NOT A SPRING you want, it is a piece of shaped wire