I don't know if there is a site just like gamiss but if you want to buy clothes with bitcoin you must exchange it first to $ and paypal as a payment method. Because most of the online shops do only accepts payment with paypal or any other authorized web site. If you are not unable to find some other site like this, well try my suggestion and use virwox for it.
Well, I also don't know if there's a site that accept bitcoin as a payment of their costumer. In addition to that, as of now there is still no online store who totally accept bitcoin. Buying clothes with bitcoin is a nice idea and by using bitcoin you pay it easily and instantly. Lastly, I believe that bitcoin will accept in all kind of commercial establishment.