I've made lots of adapters, my go to method is to get a bit of 2x2, cut a short length off to make a cube (2x2x2 if you will), and drill holes on either side - one for the tool, one for the vac.
They tend to look a bit odd but easy to get a tight fit if you've got a set of spade bits.
Bikes content ? DIY content ? Behold the great dewalt to Henry inner tube connection of 2021.
1 Attachment