In reply to LHempton:
If Marmot gloves in unisex XS fit you, that should mean (approximately) your hands are 6.5-7" around the widest point.....
If this assumption is right and you don't have especially long spindly fingers (!) then marmot womens size S gloves are 6-6.5", and their M gloves are 6.5-7" So in theory, if the XTs are a little to big, then if you got a womens size S it would be a tighter fit for you, and a womens M would be the same fit.
Outdoor research and mountain hardware gloves in womens size S start at 6.5-7" supposedly the same size as the unisex XS from Marmot.
Black diamond size their gloves a little differently, just by the width of the knuckles, rather than all around the hand, but their womens XS glove comes in at 2.75-3". (I wear BD Medium gloves (3.5-3.7"), and Marmot medium too (8")) so I'd think their W XS will fit within the 6-6.5" size range.
If a 6.5" glove is to large for you, then had you thought about kids gloves? Outdoor research do some kids gloves that at size L are 6" round, and they look fine for climbing in (e.g. Gravitator.)