I replaced mine with a screen screw kit from one of the cheapie places - MPS/M&P/Busters/etc - and these were slightly bigger so I had to just run a drill through the holes, but they worked fine and look the same.
The great thing is I took them all off to replace them with a set of black ones from TecMoto and all the rubber nuts were fine and I didn't mash a single one! Just goes to show them Italians can't make/source decent fasteners.
Cheapies cost £8 or so for a pack. I think they were Motrax so you should be able to get them from a local bike shop. TecMotos are 24.99 but are a better match for standard.
http://www.tecmoto.co.uk/ Tell them the DSC sent you!