I'll still send the OP a section of that 30g plastic tube, but I think I found a better option. Maybe a touch bigger, but much lighter.
Just got a lead-acid car battery in the mail on Friday (own a Prius, live in Alaska, you do what you have to). There was a some substanial closed-cell foam around the battery. Really stiff. In about 75 seconds, I cut it to size and whacked out a cavity to fit my glasses with a razor knife. Then I cut a piece of a much higher-density, stiffer foam as a "cover" that might be secured with a rubber band for daily use or duct tape if it was only for back up.
Total, with foam cover, 12.2 grams.
Without cover, (foam block with deep cavity for glasses): 7.1 grams.
I will send you the tube, but I've also stuffed some of that foam inside of it - enough for a glasses case.