I’d go amazon, but i guess you need it like now, so idk

If its Imperial: https://www.amazon.com/MAXCHEER-Guitar-washers-2-Conductor-Output/dp/B09LC9D8LN

If its metric: https://www.amazon.com/KAISH-Metric-Guitar-Output-Guitars/dp/B09134T91W

Maybe a hardware store? I dont know the sizes there, but I think it’s 3/8in or 12mm

Good luck, that sucks