For something like this it is best to source the "manufactured" part before you do the mod, since your options might be limited. That said, I suspect you can modify your existing hole to work well with a standard rubber grommet from Amazon, like this one:
https://www.amazon.com/Large-Rubber-...ps%2C65&sr=8-3
just search for rubber grommet and be careful to check for dimensioned drawings, since the verbal descriptions are often vague or misleading.
Good luck!