My buddy has a JessEm Rout-R Lift II he uses as part of his woodworking shop. I designed this customizable insert ring in OpenSCAD so he could print off whatever size he needs instead of having to purchase them. Pictured is an original ring (red) beside a printed one (black). Perhaps this will work in other manufacturer's router lifts and tables, perhaps not. Feel free to rework my .scad as needed for your purposes.

Print attached .stl and install in your router table. Play with the .scad file as needed (ID sets tool hole size, FL adjusts friction-lock pressure). I printed with ABS at 0.3mm layer height and 30% fill.