On Friday, September 6, 2019 at 3:30:40 PM UTC-7, Joerg wrote:
Just received a new rear wheel. Despite being 700c and for narrow tires
the rim is drilled for a Schrader valve. Couldn't believe it. Harumph,
grumble. Why on earth ... well, it is what it is.

I don't want to wait for some fancy adapter but I do not mind making
just about anything in the garage with hand tools. My special thick
tubes have Presta valves.

It's difficult to machine this adapter. Any bike shop should have those in bulk for a couple of bucks.