Grey workout jilbab from http://www.everythingislamic.com/scripts/prodView.asp?idProduct=366 for $30.99 GBP.
JUST A NOTE FROM MYSELF, when working out, I wear modest fit pants and wear a jilbab over. I cut my jilbab so that is has a side split so that is allows my movements, when running or rock climbing (which are two sports I personally do regularily). As for hijab, I tend to wear a stretchy al-amira made from swim suit material and I pin my shayla over top, partially tucky the back portion of the shayla into my clothing, and pinning the front portion with saftey pint so that id doesn't fly off my chest and over my face. Niqabis advise doing the same thing with niqab---pin it to the chest to prevent it from flying up in action.