I have one labeled shutterboss from Vello. It seems to be no longer available but it is marketed under a number of brands: Mine looks just like this one:
Amazon.com: Polaroid Shutter Release Timer Remote Control For For The Canon Digital EOS Rebel T4i (650D), T3 (1100D), T3i (600D), T1i (500D), T2i (550D), XSI (450D), XS (1000D), XTI (400D), XT (350D), 60D, G12, G11, G10, G1X Digital SLR Camera (Repla
Just make sure you get one with mini plug connection, I think it is the same as Canon, Nikon seems to use a different connector.