Video Capture Device that fits in 3.5" Bay

I am looking for a Video Capture Device that will fit into a 3.5 inch bay that includes analog inputs such as RCA and S-Video as well as firewire. I have found many that fit into a 5.25 inch bay. The problem is the school I work for bought some Dell GX620 Desktops (instead of the towers) and all they have open is the 3.5 drive bay (there is no floppy drive).