vinokilo.com if you are in Europe, they also have events in cities where they fill a space with sorted clothing and blast music way too loud (so bring earplugs)
Nice idea but the fun of vintage clothes shopping is having a few hours with nothing better to do than trying on the umpteenth ugly sweater/velvet jacket/vintage dress until you find one that looks better than one you can find in 15 minutes on the high street. Buying online is totally meaningless in the space.