This button was designed for the right side of the faucet head but I think mirror reversing it should get you a left button. Where the post from faucet is inserted into the button is slightly undersized to make it a tight fit. You might have to enlarge it slightly with a drill bit.. Just clean it out by hand, a twist or two, no need to attach it to a drill.

Is it perfect?... No but pretty close. Will it last forever... I'm on my second one, so no. But will it work for a few months before you will need to print another (I would print more than one at a time)? Most likely.

But considering it is impossible to find a replacement button, it's a decent solution.

Have a great day,

Tom