Alternatively you may be able to use these instead :     
Look under UNC Socket Cap Screws.
2-56   3/8   9.53   3/8   9.53       5   MF-SC223    £0.85   
25   MF-SC223/25    £3.50   
You'll need the required tool to mount it though, he sells good and cheap sets too but do check if the correct size is in the set...