You could look on www.trademe.co.nz in the real estate / rentals section, but these homes might be hard to get as NZ is suffering a bit of a rental shortage so anything gets rented out fast.
Possible other options would be to email some air bnb listings or from bach care and ask if they'd do a long term rental to you.
Lastly, drop a line to Rotorua Mountain bike club and see if they could put feelers out for you and maybe you could board with a club member?