Thank you for the tips here about how to check for fluid amount in a Bic. The solution was hiding in plain sight!

Another fix on the smallness of the mini Bic is to wrap the case with bike inner tube. I take smaller sized inner tube (forgot size), cut it into 1cm strips, and double up each strip around the casing. (I'm not sure if I described that well.) The whole casing can be wrapped with as much inner tube as you desire. You then have a casing with some grip to it. It's not pretty, but it's lots of functionality in a small space. Inner tube is outstanding tinder, but only for emergencies because the fumes are toxic.