Powell's Rib Bones might have gone out of fashion in the "regular" skateboarding world a couple of decades ago, but they still work! Designed to make boardsldies easier, they also protect your graphic and have a decent length to them, making them perfect for shorter longboards and bigger pool/ramp setups.
Price is for a pair of rails with mounting screws, they are super easy to install. All you need is a cross-head screwdriver - like the one on your skate tool - and you're set!