Is there an electronic cigarette that doesn't cause phlegm?

No: the only area where electronic cigarettes may be somewhat safer is in it the reduced amount of "tars" - complex hydrocarbons produced by burning of the tobacco- found in them. However, they still have many irritants, and many of them (like propylene glycol, used as the propellant) have unknown effects when volatilized, which is true also of the flavorings, colorings, preservatives etc in them.