Not sure exactly what kind you are looking for but Regal (Bath Ave) Aquariums has a full koi tank. Hit them up. He said in an earlier post he is closed today but should be back open Friday.
Take a ride to LONG ISLAND Kodama Koi Garden just opened you will not be disappointed .
Beautiful koi decent prices.I have 20 Koi and couldnt help my self brought 3 more
Here is their address
Woodside Nursery sand garden center
134 east woodside ave
Patchogue NY 117722
ph 631 438 0788
We sell koi as well, I typically bring in Israeli Koi, the color of them is really nice and the price is spot on. I can do a 16" or about $199 I also have smaller sizes available.