5/8 line.

I have 1/2 valves (manifold) so i decided to buy 5/8's line. A friend then decided to tell me that its gonna be hard for me to find fittings for 5/8 line. Anybody know where to find the fittings. Is there any way i can make the dump ports smaller? i want it to go up fast but i dont want it coming down that fast. Thanx