Spray can holder push-pin adjustable mount and union

My son kept messing with all my spray cans so I saw this and said, hey, this is great! I'll print like 8 of them. And I did, and then I looked at the remixes

So I didn't want to drive huge screws into my wall (they have to be huge if the cap is going to be big enough to hold the half-hole mount) and I didn't want to drive even more huge screws into my wall if I wanted to adjust the width of the brackets

So the solution? Push-pins and a slide rail! And if you're even more ocd than me, a uni