My lawn tractor cupholder not only didn't print so well (I was a real SketchUp newbie at the time), it didn't stay on my lawnmower very well. It was designed to sit on the button at the end of the deck height lever, and that button's not a great place to mount a cupholder -- it's too easy for it to fall off. I mean, it was good enough, but I knew I could do better.
This is me doing better. The key difference is that this one mounts not on the button, but around the rubber handle, below the button. Not only does this mean the button remains accessible, it's a much better grip. But since the handle has a lip at the top, I couldn't just use a loop that slides down onto it, so I had to use a different design.
First, the "sleeve" part that sits around the handle has to be tapered, since the handle itself flares towards the bottom. While the outside of that ring is a cylinder, the inside is a frustum -- the bit of a cone you get if you lop off the top. Second, I had to split the sleeve into two parts, and put in bolt-holes and countersinks for the nuts. (If I had it to do again I'd probably put the countersinks on the opposite side from where I did.)
The result is a cupholder that mounts permanently, still lets me operate the deck control while it's on, and holds nice and firm. It does require a pair of #6-32 half-inch round-head bolts, and nuts to go with them, but no other hardware.
In case you're wondering, it's not sized to hold a can of soda (or, heaven forbid, beer -- yuck!) since it counts on the cup that's in it flaring towards the top to hold itself in.
The main body needs to be printed with supports.