Finn.no without bankID

Hey! I'll be an erasmus student in oslo and I'm trying to contact a seller through finn.no to buy a router for kringsja residence, but it seems that I cannot message people if I don't have a bankID. Does anyone know an alternative second-hand app or any way to use finn.no without bank ID? I'm only staying for 5 months so I don't wanna spend much on a new router, so cheap router recommendations and where to buy one are also appreciated

Tusen takk!