>>33938382I usually ask ashdrs(dotcom) myself to get me the doujins and other things (though he has a few barriers to avoid "&!@" people), but you can google japan proxy service or something like that and will get you a few results (expect poorly made sites/blogs, "engrish" and a few professional sites that usually shop for you but attend events).
Most places also allow buying from yahoo auctions and doujins are usually cheap there shortly after any event that featured it ends, unless you look for some "unobtainum" doujin that is greatly coveted for other overseas buyers.