Just use large penny washers and two screws. Stainless steel would be the better option but more expensive.
Cheaper option
Need a secure and lasting fastening from your nuts and bolts? Use these penny washers to distribute the load evenly beneath the bolt head or nut face - fixings will be less likely to loosen over time.With a 25mm outer diameter and 1.5mm thickness, these M5 washers will also help to prevent...
www.toolstation.com
The above are 25mm, it doesn't matter too much if the washers are slightly smaller than the holes, they will be large enough to "grab" the pot. Don't over tighten them though.