does anyone have an answer for this?

It depends upon what gauge you have, etc. For example in my case, I have a 4' braided hose that screws directly into the back of the AM gauge. I have a couple of adapters to go from the 1/16" (IIRC) Schrader valve to the braided line (4 AN IIRC). You just look at what you have and get adapters to get there.

Fuel pressure gauge adapter fittings:
http://www.holley.com/products.asp?product=17945NOS AN 4 to 1/16” pipe
http://www.holley.com/products.asp?product=16785NOS 1/16” male pipe to 1/8” female pipe

Or
See http://www.autometer.com/cat_accessorieslist.aspx?pid=10

You can buy the Autometer Stainless Steel braided hose for like $60. Or a local shop that makes hydraulic hose assemblies can make it for you at a cheaper price. Ordinary low pressure hydraulic hose can be used in place of the Stainless Steel braided hose, the Stainless Steel braided hose just looks nice. I got mine for $4 at a place that sells industrial and military surplus parts of all kinds. The Stainless Steel braided hose goes for about $3.60 a foot and the fittings are probably about $5-$8 each. You can make your own and save some $$$, the shops may have a setup or labor charge to fabricate the hose assembly.