Carnatic Music has not exactly made its way to mainstream American music stores. Though on various occasions music is available from some of the larger stores like the Virgin Megastore or Tower Records. Look in the Asian or Indian section. Expect there to be a slight markup, anywhere from $1 to $4.
If you go to Carnatic concerts or Indian Cultural events then you are bound to find travelling dealers. They carry a wide variety of CD's and tapes and if requested can get any number of recordings. There prices are competetive however they can be slightly more expensive then wholesalers.
Over the Internet, it is very easy to obtain Carnatic music. Huge stores have web pages with large searchable databases. Again if they do not have the CD then they can obtain it for you. Their prices are competetive and some offer price protection and various guarantees. The three best are Raj Music , H & M , and Khazana (my personal favorite).
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