I have a 2015 KoAloha that is all Koa, however I know they have gone away from that. I don't know of any company that makes all Koa ukes anymore, however, I am sure you could contact a luthier and they might make one to your specifications. The 16" Ono I just had made has an all Koa body and neck. I went with ebony for the fretboard, but the beauty of having a custom built is that you can get it made to your specifications.
Soprano: Late 20s Martin Style 0 | Gold Label Kamaka | Early 20s Lyon & Healy Washburn | Ohana SK-25 | Outdoor Ukulele - bottle green
Concert: 16" Ono | Talsma 3M | Howlett Koa Ditson | Blackbird Clara | Ono Pineapple | KoAloha KCM-00 | VW Flea
Baritone: Kala KA-ABP-CTG | Bonanza #38