I don't know the exact location on the Dina. But they are generally located on or near the brake valve.
Follow the linkage from the brake pedal to the air valve and there should be a pressure switch that screws into the air system that will have 2 wires attached to it. That would be your brake light switch.
JD is an excellent source for replacements for these as he has found a aftermarket switch that is about 1/2 price of OEM. Might want to stop in and see him and ask to look at one so you'll know what it looks like when you find it. (shoot I would go ahead and pick one up to keep for a spare incase you ever need it on the road!)