Are you wanting to use the insulator going forward or no?
I would go with a mm set...basically as faceless said the wick hole is 3.08mm so if you find a 3mm drill bit that's pretty good...I have a 1/8th inch which is 3.1mm that fits but that could be a manufacturing tolerance and not all 1/8th may fit since technically they would be a .02 of a mm larger.
Not really sure what the internal diameter of the insulator is.
Edit: Give me a moment to go to the garage and find a drill bit that fits
through the insulator.
Ok I have one that fits but I have no idea what the size is, it has no writing on it at all and my digital caliper is out of commission.