Very cool! You’re just going to tease us with those right? 
I traveled across continents, road a donkey up the side of a mountain, and had to learn Chinese to find these... made of the world's finest chinesium via Ali Express. I ordered them a last Sunday and they showed up on a Saturday morning on my doorstep. A little over 6 bucks for 10 of them, delivered in 6 days from the other side of the world. Crazy.
The head of the Tube Connector is a little over 15mm in diameter. The main body of the Tube Connector is +/- 11mm in diameter. I think the body may have varied in diameter over time to facilitate some compression of the inner tube. I think I read that on the internet, so it must be true. See the drawing / specs below. I figured these would work by drilling out the center with an 11mm drill bit, and as long as the head was really 16mm ID, the Tube Connector head would fit perfectly. It was high risk, but my 6 dollar bet paid off. The store name is below, but I think many storefronts sell them, and who knows how long this one will exist. Pay attention to those measurements (or measure yours) as there are other version of these aluminum washers... spherical, etc. I thought this conical shape would look the most "right".
