Where do I order USCG fuel line and press on fittings? Do the lines from the Separator and pump need to be solid?

For Fittings... try Maryland Metrics....

I was looking for the same info, what I found in coast guard regs is that you can you rubber line but it must be u.s.c.g approved type A1, for all fuel lines.

They sell 3/8" ($1.99/ft) through 5/8" type A1 at Boater's World.

Line from pump to carb should be solid. Rubber lines can be used everywhere else but they still have to be USCG approved.
Solid line will have inverted flair ends. You can make your own with a bender and flair tool or buy pre-flaired lines of various lengths at auto parts stores.
Gary