You may download the manual (adobe pdf reader needed) here.
http://www.dxgusa.com/Support/Manual...dxg308_eng.pdf
And it says it uses SD cards. The max size is a 512 MB card, but maybe when the manual was printed, 512MB was the largest available. These days, that is about the smallest one you can find. Anyway, look for a 512MB SD (Secure Digital) card.
In Tacoma, WA, Walgreens probably has them. Also Office Max, Office Depot. Best Buy, etc. Probably around $10-20 and probably lower.
P.S. None of us work here or run this website. Just passing thru and don't mind answering newbie queries.