Saved from buying another $25 pump for want of a 25 cent replacement part.
I had a flat tire on the way to work today. No problem. Set to fixing, a few minutes later, discovered that the compression cap has gone missing from the pump. Topeak will probably replace it but I decided to see if I can print threaded parts - I have had trouble in the past but my printer is now much better tuned.
To my surprise it worked great. The threads are 14mm x 1mm, printed at 0.1mm layer height. It just screwed right on and works fine.