Since I can't seem to find any official Doser Lever Springs here in the Netherlands, my quest for the right spring moves on to the DIY stores. What exactly is the size of this spring? Can anyone measure the spring next time you service your machine?

The spring on mine broke about 2 weeks ago and I replaced it with a generic one from my automotive collection. The length and tension aren't critical - I found one in my spring drawer that was about 1.5" / 40 mm long with a 360 degree loop at either end, and it works fine. But I could have used any length from an inch / 25mm to almost 2" / 50mm as long as the tension was low enough for smooth operation but high enough to pull the lever home after each dose. The diameter of the coil itself was probably about 3/16" - I'm sorry, but I reassembled it and disgarded the broken spring, so I can't give you exact measurements. It's not critical as long as it stays in place and does the job.

I suspect that softer is better than stiffer - the design flexes the spring where it bends into the end loops, so too much tension probably hastens breakage of the spring and/or the plastic pegs that secure it. Take the broken one with you as a guide to tension. The one I used is the length of the largest one and the diameter of the middle one - the hand gives you size perspective:

Any pulling spring slighty shorter than the distance between the mounting holes will do.
The tension of the spring is a matter of preferences, some like a strong, some like a weak pullback on the lever.

If you prefer weak, you can even use a pushing spring and bend it into form.

Thank you. My automotive collection is very minimal. I'll have a look into my children's toys... should be somthing with a spring.

I've seen ballpoint pen springs that would do the job if you bend the end coils 90 degrees to the axis. The correct ones are larger diameter than most because they go around the barrel of a large refill.