Autometer Oil Pressure gauge hose

http://www.jegs.com/i/Auto-Meter/105/3224/10002/-1
or
http://www.jegs.com/i/Auto-Meter/105/3223/10002/-1

Connect the flex tubing or hydraulic hose to the gauge restrictor. Be sure to route the tubing or hose away from the exhaust manifolds. Be sure to either use hydraulic hose or oil and heat resistant flex tubing for the pressure line. Do not use copper tubing for the connection to the gauge restrictor or engine. Over a period of time, the vibration will work harden the tubing and cause it to crack and fail.

Any place that makes hydraulic lines can make your oil pressure gauge line. They can make just about any kind of line you want.

Be sure to use a gauge restrictor fitting in the pressure line going to the gauge. The restrictor will prevent all of the engine's oil supply from ending up on the pavement before you can stop it if the gauge line fails. I had a gauge line rupture, and the restrictor fitting saved my engine from serious damage.