Trying to locate info on Zephyr motors

[AcecaRacer]

Fellow AC owners,
   
   I have a racing 57 Aceca with a Bristol D2 motor.  I would like to pull the D2 out and replace it with a 2.6 Zephyr for more power in period.
   
   As I am located in the US (California) info is limited on locating one.  Does anyone have any info on a US based provider?  UK provider?  Ease of parts access (or lack thereof).
   
   Any info on this topic would be greatly appreciated.
   
   Cheers,
   Rob