There's a good little place in Waikiki, on the corner of Koa Ave & Uluniu Ave, down stairs from the La Cucaracha Mexican Bar. It's 1 block back from the beach.
www.google.com:443/mapscorner of koa ave, and uluniu ave, waikiki, hi
They do board hire. You pay for a whole week, and reserve a board, or try different boards. They had SUP's, and they probably have more now.
Man, Steet View is crystal clear here.... you'd be able to see the hire rates in the window, if Google hadn't have smudged the info out !
Here's a street view screen grab. It's in the sunken forecourt. You just leave your board at their place when you are not surfing!