I struggled with that same issue for a long time. I haven't found anyplace local. I will purchase in bulk at The Makeup Show, IBS Show or various beauty supply wholesalers in NYC. If you walk around midtown Manhattan (27-29th & Broadway or 7th Ave), you are destined to find a few scattered beauty wholesale spots.
You can also try http://www.eeyelash.com or www.madamemadeline.com, Ebay and BundleMonster.