Common place in Japan, but sometimes difficult in the USA to source.  This JDM 1/8PT (or as better known in the USA 1/8 BSP British Standard Pipe) are common thread sizes for many Japanese makes, including GReddy.  This is common for sensors, oil cooler adapters, oil lines, water lines and vacuum lines. 
           (*this is NOT the same as 1/8NPT, which is more common in the USA)

GReddy 1/8 Hose fitting - straight

   11900645 - JDM 1/8PT (1/8BSP-in the USA) Vacuum Hose Fitting - 5mm nipple
   11900648 - JDM 1/8PT (1/8BSP-in the USA) Vacuum Hose Fitting - 6mm nipple. (BOV)
   11900651  - JDM 1/8PT (1/8BSP-in the USA) Vacuum Hose Fitting - 8mm nipple
   11900653 - JDM 1/8PT (1/8BSP-in the USA) Vacuum Hose Fitting - 10mm nipple

   11908601 - JDM 1/8PT (1/8BSP-in the USA) to -3AN Fitting - Aluminum (blk) - NEW
   11908602 - JDM 1/8PT (1/8BSP-in the USA) to -4AN Fitting - Aluminum (blk) - NEW
   11908610 - JDM 1/8PT (1/8BSP) to Female 1/8NPT Adapter - Aluminum (blk) - NEW

   11900561 - JDM 1/8PT (1/8BSP) Male to JDM 1/8PT (1/8BSP) Male Union

GReddy 1/8 Hose fitting - plug

   11900670 - JDM 1/8PT (1/8BSP-in the USA) plug fitting bolt (hex)
   11900672 - JDM 1/8PT (1/8BSP-in the USA) plug fitting (allen)

GReddy 1/8 Hose fitting - 90 swivel

   11900620 - JDM 1/8PT (1/8BSP-in the USA) 90 Vacuum Hose Fitting - 5mm nipple
   11900621 - JDM 1/8PT (1/8BSP-in the USA) 90 Vacuum Hose Fitting - 6mm nipple
   11900622  - JDM 1/8PT (1/8BSP-in the USA) 90 Vacuum Hose Fitting  - 8mm nipple
   11900624 - JDM 1/8PT (1/8BSP-in the USA) 90 Vacuum Hose Fitting - 10mm nipple