Is there something that would allow humans to travel in & out of faerie at will?

It's for a short story I'm writing. Is there anything in legend & lore, or could any of you think of something that would allow a human to travel in and out of faerie at will? I am actually trying to create something for my character to use - perhaps an artifact of some sort. It would be given to the character BY the fay so it cannot be harmful to faerie or it's inhabitants. Ideally it would also keep the character from falling victim to the time differences between world. Any help would be much appreciated! :D