Just received said bike and I know it's not all too common.
I see Lucy Charles-Barclay and Frederic Funk having like a custom (metal?) rod bottle adaptor stuck in the saddle adaptor hole. Does anyone know what this is and where to get it before I start experimenting with custom solutions.

Looks like Lucy in Kona used already a more updated solution, closer to the saddle, however there's some sod of rod still stuck in the saddle post.


Here's also the older setup similar to Funk: