I see the problem now with your original question.. Those aren't 3 1/2" hard drive bays but the typical 5 1/4" bays commonly used for optical drives like cd rom, cd writers, dvd rom, and dvd rw types. That makes more sense since you were off on measurements.
If the card reader is a 3.5" device then you would need a drive bay adapter like the ones used for seeing a hard drive placed in one of the top bays. Those are usually low cost items found at most online vendors like newegg or some other place in the accessories section.
Take a look at what newegg sees there for one to gasp for air on their price thougn.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811993007
I guess newegg is far from the cheapest on everything.
http://www.thenerds.net/STARTECHCOM...ode=cii_9324560&cpncode=11-43903536-2&affid=3
Besides the typical two piece tray/face plate combo there are also the two piece metal bracket types like the one seen at
http://www.techforless.com/cgi-bin/tech4less/104437?mv_pc=nextag
Those are a little more awkward to work with but leave the face plate area empty for installing things behind a cover over then a floppy type drive where nothing is exposed.