For those of you who dig the '40/'50s style handlebar mount bottle cages, Steel-Vintage has single and double steel types in stock. Shipping is 20-some-odd bucks but it doesn't increase much for multiple items. I purchased the same model from them a year or so back and another set from an Italian vendor last month when SVB didn't have them - price was about the same.

I used a double on my '54 Holdsworth, took a little fiddling with to make perfect but overall not bad.
https://steel-vintage.com/collections/bottle-cages