A picture, I cannot draw; but I can describe how I replace one of those springs. I snip off 6" or so of small gauge brass spring wire, then wrap it twice around the counter-finger-thingy, leaving an 1/2 inch or so left over. I then twist together the 1/2" piece and the main bit like a twist-tie and cut the excess off the shorter piece.
Next comes the hard part: determining which way to wind the wire around the arbor. I give it my best guess, then test it by pulling on the end of the wire. If the pull causes the lever to move downwards, then I wrap it another six or seven times and tie it off on the nearest movement pillar. (If the pull causes the lever to move UPWARDS, then I unwrap the spring wire and re-wrap it in the other direction.)
The diameter of the wrapping is fairly well determined by the gauge of the wire and not something to worry about. Worry about this instead: make sure that the lever can be moved upwards easily (is not constrained unduly by your spring). The spring is really just a gentle aid to gravity & not meant to have great power.
Best of luck.
~Jonathan
