Screw around with a fresh set of nuts and bolts. For your clean popsicle you pick a nice set of 7/8 or 1 Inch. Depending on the height of your risers you choose longer hardware; for a 1/8 riser 1 to 1.25 Inch will do, 1/4 risers need 1.25 Inch screws and 1/2 risers stay put with a set of 1.5 Inch hardware.  

For your longboarding needs you might need longer screws, depending on the thickness of your board.