For the 18 and 22s the plug sizing are as follows: For the 14 version I`m not sure of the exact size..
Everbilt-3/4" -in-Nickel-Plated-Steel-Hole-Plug-13118/202209533 are the ones at Home Depot and run about $1.70 each
Mcmaster-carr.-----Push-in Metal Plug, Nickel-Plated, Fits 3/4" ID, 59/64"...