“My job requires me to attend lots of boring lectures and conferences. Knitting keeps me focused, but my employer won’t let me knit. What else might help?”
Have you explained to your boss how a “mindless activity,” like knitting, helps you sit quietly and focus on the speaker?
If he still says no to knitting, find another activity that is a bit more discreet-fiddling with linked paperclips, playing with a loop of yarn, or taking notes and doodling on the page could do the trick. Experiment to find the “fidget” that works best for you.