Sound hole diameter of f47ce 1999 Westerly Rhode Island

[Kelly K]

Hi there. I have recently aquired a F47ce 1999 Westerly. I tried to play it live, plugged in without a sound hole mute and the feedback was horrendous. I’m trying to find a sound hole mute that will fit this guitar in diameter and depth. My measurement with a soft tape was 3.54” is this accurate and where can I find one with an odd size diameter. Most on market are 86 mm or 100mm. Any suggestions would be appreciated. Thanks!