Okay, here's a freehand sketch of the side view of the filter drawer. The handle is a flat plate that goes the whole width of the filter drawer with a little lip at about a 45-degree angle at the bottom as shown, and the handle plate is attached to the drawer with screws through those two little holes that screw into a square plastic piece that's as thick as it is wide (the same thickness as the filter drawer). To pull out the drawer, you press in on the panel that covers the condensers and grab that angled lip underneath.
So what you need to do is get a square wooden rod, maybe 5mm on a side and glue it to a wooden plate, made from modeling plywood or maybe even a piece of plastic, and another piece at the bottom to serve as the lip, which blocks light from the bottom of the drawer. There's also a strip of light-trap fabric on the top part of the plate that keeps light from getting out the top. You can get light trap material from www.micro-tools.com. Make this handle piece the width of the filter drawer, screw it in, and you're in business.