You've got six options:
1. Babolat Skin Feel - a touch thicker and heavier than stock grip. Surface is very similar to Gamma Hi-Tech replacement grip, so you could play it without an over grip. Bevels are quite sharp, but with an over grip Skin Feel is very nice.
2. Prince Resi-Thin - also a bit thicker and heavier than stock grip. Surface is soft but not mushy. If you sweat this one becomes very slick. Feels OK with over grip on top, but maybe a bit mushy if one is used to leather + over grip.
3. Tourna Pro Thin - a bit thinner than the stock grip. Same weight. Has a perforated and tacky surface that feels low-quality to me. I would use this with an over grip. This very thin grip has some substance but it leaves the bevels feeling very sharp, almost like if you had just put one over grip over the bare handle.
4. **** Synthetic Leather - I haven't tried this one but understand it to be as thin as Pro Thin (that is, as thin as they come) and weigh about the same. It is meant to be used with an overgrip and apparently feels very similar to leather+overgrip when used this way. Very expensive!
5. Wilson Feather Thin - a new product that TW does not yet stock. A guy in another thread said it was about as heavy and thin as Tourna Pro Thin. Apparently tacky.
6. Two overgrips. This is actually what I'm favoring at the moment, but hoping that **** is worth the bloody money. Wrap the first one double-thick, so that the overlap is almost one-half the width of the grip. This way, instead of an overlap you actually get a slight gap that is reminiscent of the depression in a leather grip where the edges come together. It won't make it all the way up the handle, so this is really an option for a single-handed player. So the first over grip is double-thick, then the second goes on normally over the top of that, making for three thicknesses of over grip. This is just a hair smaller than the Yonex stock grip + over grip and feels very nice. The bevels remain a bit sharper than I prefer, but as you can tell by now I'm kind of girly about this stuff.