Try searching for R2556B-8 or R2556B-9, these are the 8 & 9 heat range plugs for the 4B11. Try asking a local NGK dealer to see if they can order them for you.

The number 9s were out of stock here in Japan for 2 months. This was due to a famous Evo tuner here mentioning the breaking of ceramic insulators on the stock type plug. It kinda caused a minor panic and owners were all buying them.

*Edit, attached a better close up picture of the actual 4B11 Racing Plug.
** Added another side by side pic to compare the two.

 

WOW! I just called NGK.com (888-800-9629) and they have the 9 heat range race plug in stock. She has 8 plugs and they go for $98 each.

$400 bucks for 4 spark plugs. I'd rather try and find someone to ship them to me from japan.