It's 1/4" OD, inverted flare (brake line style) fittings, and no longer available from GM. NAPA wouldn't have it.
Even if you're skilled at tube bending, I bet you'd screw up a few before you got the intricate bending correct.
Kirban sells these tubes. I recently bought one and held it up to my original oil tube -- it looks a DARN good match. About $30.