Gday,
Lake Taupo is awesome, get back there as often as i can, its my hometown before moving to AUS 28 yrs ago. and like said above Acacia bay is just an amazing place 5 mins drive away. My uncle has just sold his place and moved back into town...stupid move.
try this place
http://www.boatinglaketaupo.co.nz/sups.html and search on facebook SUP Taupo and message them and have a chat. My aunty hired a board on the lake just a couple of weeks ago so its definitely possible to have a SUP on the lake.
Also these guys, not sure if they hire though
www.boardridersnz.co.nz/ Cheers