Where can i get the MT-card for my Nintendo 3DS In USA ?

  My Nintendo 3DS was bought in March 2014, its version was V4.5 when i got it , my cousin told me not to update the firmware to the latest version , i was been told that i can not play 3ds games on it if i do that.But every time when i conncet to the wifi ,the console reminds me  to update to the latest firmware version , which is V7.2.0-17 now .Of course i didn't do that .
   I used the r4i gold 3ds flashcart to play ds games on my 3DS before , now i really want to experience playing 3ds games on it , because i saw some of my friends play the cool pokemon X/Y with a special card , 3ds flashcart i guess . What's more , my 3DS firmware can work with it , that is terrific !
   After serveral hours' google ,i found this one is great : MT-card , and some of my friend also use it , so i decided to get it ! it arrived door within 4 working days due to they based on USA , and provide free shipping for all items , it only cost me US$68 , it really save me a lot of money ! Since i am a noob to this kind of flashcart , and it is kind of complicated to set up it , the reseller send me the step by step user guide via firmware donwload link to me , What's more , i ask then to send me  serveral my favourite 3ds games , they did it !  What a surprise !