Lawn Mower Handle Replacement Knob

I lost 2 of the bolts that hold my fold-able lawnmower handle together. After searching for Things, I decided to try Tinkercad.com and design my own. Nothing fancy here, just practical.
I thickened the top, bottom and side layers to give a bit more rigidity. I purchased the nuts and bolts from Home Depot for just a few dollar$. I could refine this piece, but it's an outdoor item I won't be using very much. It is what it is.

I printed the knob with PLA and it lasted for a whole year. I would recommend using PETG and giving it an infill of at least 50%.

Bolt: 5/16 in. -18 x 2 in. Carriage Bolt
https://www.homedepot.com/p/Everbilt-5-16-in-18-tpi-x-2-in-Zinc-Plated-Carriage-Bolt-800146/204633685 

Nut: 5/16 in. -18 tpi Coarse Zinc-Plated Steel Jam Nuts
https://www.homedepot.com/p/5-16-in-18-tpi-Coarse-Zinc-Plated-Steel-Jam-Nuts-8-Pack-811541/204274137?keyword=jam+nuts+315347&semanticToken=v00b000002+%3E++st%3A%7Bjam+nuts+315347%7D%3Ast+f%3A%7Bv%7D+m%3A%7B1%7D+cnv%3A%7B8%3A1%7D+vc%3A%7B1%7D+oos%3A%7B0%3A1%7D+qu%3A%7Bjam+nuts+315347%7D%3Aqu

UPDATE
After a summer of mowing my lawn, I've decided to update the handle to fit my mower better. The file with "final" in the title is the updated mower knob. I have also found better bolts from Ace Hardware that have a curved head and stay tighter in place.
The nut fits really snug, just make sure your bolt is long enough to fit through the knob and handle.