The outside circumference of my base is 48", which gives a diameter of 15.29" . The drain is a little more than the width of my thumb from the base, the base is about 5 inches tall.
If rust is not an issue, I would pick up an old 15" tire rim with at least a four inch set back (distance from the rim edge to the bolt plate/holes on the back of the rim). There might be an issue with how high it sits.
Another option would be to cut a hole in plywood, using a 7.64" radius and build legs with 2x4s, blocks, bricks, whatever.
Disclaimer: I measure once and cut a lot, verify these measurements before proceeding!