What spring for Greg Wade extruder?

I'm just wondering if anyone has a recommendation for which spring to use with this extruder?

[www.thingiverse.com]

I looks like I need about a 1" spring and I'm sure many different kinds would work but McMaster has 1" springs with strengths from less than 1 lb/in to over 30 lb/ in. See here:

[www.mcmaster.com]

I have a feeling something in the 8 lb/in range should work fine but I thought I would ask. If I had a fishscale I should measure the spring off my other printer, but I don't have one. Any suggestions?

...or I could go to home depot and see if they have anything that might work. Thanks for any advice.

it is 1.2mm spring 20mm long 7.5mmOD and 5mm ID

Dear RDM6!
I put springs from Presa clothespins in my extruder. They are a little bit to stiff but they will do the job. I found them in Ikea for about $1. And I think that there were like 50 pins so...plenty enough for heated bed and extruders as well.
Best regards!
Bobby