I got and mrd-m605 with the cover but there are 2 hexagonal screws that hold the cover in place and I don't have them. Where can I find those?

 

try a local nut and bolt supply house.
they will probably be called a metric hex head cap screw, sized about M2x0.75 although i could be wrong.
take the amp in or find a friendly counter man who is willing to let you take some screws out to the car and test fit.

 

Alpines authorized service centre is up here in Markham. The guys at the counter are pretty good. You can find thier name address on the alpine site.
Or, canadian tire has a good supply of metric hardware.