some times ago I had such a spring for sale coming from a gunmaker estate, think its gone for +/- 150 euro

my gunmaker had a parabellum hunting carbine projekt on stock for me

9mm DWM action allready with the long barrel but not ready. talked with mister wagner about it and he will make it ready for relativly small money. this would be a pistol I can shoot until the barrel glows.

Mister Wagner making such replicas with original DWM Parabellum actions for many years
http://www.wagner-eltze.de/waffen/aktion-lugerjagdkarabiner/