Wolff is the only way to go for springs, although a lot of other dealers may carry some of them, only the online Wolff store will have all the different combinations, including the little springs Brownells or Midway don't bother with.
I bought one complete factory-stock replacement set of everything, along with reduced power recoil, hammer, and firing pin springs from 16-12 pounds. Cost about $70, but I don't have to sweat springs any more, at least for the PPK. They won't be getting any cheaper.
Reading.... Seems factory spring is #20 and folks are going down to #17 on recoil and hammer springs for factory self defense rounds like my 90gr hydra shoks.... Found spring sets and individual springs at gun springs.com, midway and brownells as well most are Wolff manufacture.
Seems the interarms variants are good quality, as you know and have stated here the inox variants are / have razor sharp gotcha’s where ya least expect them.
Ordered a Brownell’s set of wolff’s “calibration” recoil and hammer springs, 3 of each weight, 17, 14, 12 I think are rates.... and a gun springs .com complete set of “all” stock springs to keep on hand.
I would like to pick up spare firing pin and extractors in time...
Good last few weeks of winter (here in Texas anyway) project.... Parts ordered, up to the ups brown shirts now to deliver.
Grateful for your help.
Stay safe. !