Yes, this may be the most on-brand hipster consumer product ad imaginable, and no, a sippy cup lid for your drinking jar does not deserve the glamorous electro and lens flares treatment it gets here, but hot damn if it isn't a pretty good idea.
It's called CUPPOW, and solves what its creators call the only major problem with using jars as travel mugs: "with their large openings, canning jars are not great for spill-free sipping while on the move." It was designed by a bunch of friends in Somerville, MA, is manufactured in the USA, and costs eight bucks. The only thing missing is a sleeve to keep your hands protected when you carry around a glass jar of hot coffee.
And before you write the whole "drinking out of jars" thing off as psuedo-rustic unrealistic hipster whimsy, remember that even Elvis knew that jar-drinking was a thing.