kitcarbp,
There are AN fittings available with "captive O-rings". See
http://www.hydratechbraking.com/prod...cessories.html
Scroll down to numbers 9405 and ff near the lower part of the page.
These may not be the sizes you need, but such things do seem to work - these are for power steering which uses pretty high pressures; greater than 800 psi. The facing surface for these is flat - no matching groove.
Perhaps this can lead you in a productive direction.
Tom