Spigot Gamemode Changer 1.3

I'm looking for a way to allow players to change their own gamemodes. We're running a Spigot 1.8 with GriefPrevention, Creative by default.

I've used command blocks to allow them to switch, but seems I have to give them op level permissions for them to activate - perhaps any ideas here, or a mod (or way) to just give them the option to manage for themselves.