you can get 3mm quartz tube from **LINK**
at least they list it, a phone call would confirm stock and minimum order, and whether it is suitable for gauge glass
and http://www.glass-solutions.com/wp-content/uploads/2018/09/Glass-Solutions-Tubing-and-Rod-Price-List-2018.pdf
list 3mm borosilicate (pyrex) but they seem to want to sell an awful lot at once, again a phone call might extract an odd bit as a sample
However the hole up the middle is only 1/16" so as others have said I wouldn't rely on it giving the right reading, capilliary rise will be substantial before you start on bubbles.
Edited By duncan webster on 31/12/2018 17:29:31
Edited By duncan webster on 31/12/2018 17:31:07