Here's my custom build based on a 50's swedish Monark bike. Parts from the 20's to present time. Started of as a banged up empty frame. Inspired by US, french and some swedish streamliner/beach cruiser bikes. Hope you like it!
The valve caps are available- they fit Woods valves, which are supposed to have Presta threads. I have not checked. https://velo-classic.de/oxid2/Fahrrad-oxid/Ventile-u-Zubehoer/Ventilkappe-mit-Kettchen.html
The valve cap are NOS ones, used on standard swedish bikes pre ca 1930. But as mentioned, new ones is made. The handles are made of red transparent plastic, specially made for a 50's handle bar with built in lamps for turn flashers. The idea was that the whole handle would blink red and would be visible from all the way around the bike. Didn't became a hit through.