I have my doubts you'll get one much over 2 meters. About the longest I've seen was the old benbo ones. Built like a tank I have it in the studio though so I cant measure it today. I would guess you could make an addaptor to fit onto a normal monopod giving you and extra length.
Ok I'm courious why do you need one 3 meters long?
How about a boom mike pole - they can be really long
Or this? https://www.wickes.co.uk/Wickes-Tra...xYcWS5f73__ZzqgSdY6Bg2NiG0KzT0qBoC1nkQAvD_BwE
Only 2.4m, but strong and cheap.