you can do like almost everyone who had the mini sd version (myself for example) is to get a micro sd to mini sd adapter...
i did get a 512mg mini sd (1 euro for it, found on ebay equivalent website) but the new update break the support for that mini sd card.. so now i use an adapter with a 1\2gb micro sd card
but i would go with the black version, seems more nice and no need for adapter..
you can get a ez iv from official gbatemp sponsor
http://nds-card.com/
i would recommend other stores as well but the ones i can recommend don't sell ez flash iv...
i would like to give a try to order from shop 01 media.. if you think about ordering from it, mail them asking if they are in business..
http://www.shop01media.com/en/Nintendo-GBA/GameBoy-Flash-Carts
but i am not sure if they are reliable\trustable... since i never ordered from them or heard someone order from them..
if i were you i would get it from nds-card, it can take 45 days but its a trusted store...