I ordered a bunch of spare parts from
http://www.blazingtoys.com/ a few weeks ago. The guy I emailed there was excellent to deal with. Normally I'd buy Canadian but there aren't any ICS distributors in Canada anymore so I chose these folks after emailing 3 different dealers in the US. They carry all sorts of small parts that are good to have handy in case you lose or break anything. I only ordered internals for my ICS M4 so there were no customs problems. The shipment came in very fast as well.