wow... $32 for 5 screws?!?!? ... talking about getting screwed
To the OP - any standard HD mounting screw will do. The screws on the MP come with an isolation rubber pad. Here are some that should fit and do the job.... and at a fair price
http://www.amazon.co.uk/Lian-Li-Vibration-Mounting-Screw/dp/B003MAAYLU
They are not as "fancy" as the original ones - I guess that's why its so easy to chew them up just by using a slightly larger screwdriver... but once you put the HD in the MP, you wont notice them.
There are silver colored screws available too. You should be able to get them there in most computer component stores, or google something like
this, (HDD mounting screws anti vibration).
cheers!