do you like coffee or booze? some nice coffee beans (like real blue mountain or organic something) or a good bottle of something you would never buy yourself (like 30 year old single malt, or cask strength single malt).
Your hobby stuff sounds pretty personal and that you buy whatever it is you want anyway. A gift certificate to REI doesn’t do it?
How about some sexy lengerie? (sp?) It’s a gift for you after all 
Tell her you want something consumable. I know my family doesn’t need more crap cluttering up their houses so I tend to try to get consumable things for gift giving as often as possible. This year for one of his gifts my dad is getting the sampler pack of bacon salt and I special ordered a 6 pack of my mother’s favorite soda from her childhood that isn’t available where they live.
Maybe a box of Godiva truffles would be right up your alley, or perhaps some really nice cigars? I’m sure you can find something you would like that wouldn’t clutter up your life but is still something she could wrap and put under the tree.
She could get you a nice picture frame and put a brochure, tickets or info for a dinner, concert or some kind of adventure in it. Then you could have a nice picture taken when you go to the event and put it in the frame afterward. She gets to buy you a tangible gift and you get to do something fun and have something that doesn’t take up a lot of room at home. Plus, it could bring to mind pleasant memories whenever you look at it.