Bicycle rear rack dropout adapter

I wanted to mount a rear rack on my bicycle, which did does not have eyelets on the dropouts nor is the frame appropriate for p-clamps (it's a bamboo frame).

Folks at the local shop had an idea to use a special nut designed to add a derailleur to old horizontal dropouts as an attachment point. However, this made the rack a bit closer to the rear wheel than I'd prefer—it prevented adding a rear fender.

These adapters attach to the rack and provide a bolt hole for the dropout mount. They s