According to the schematic, it is a 500mA fuse:http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdfJust replace with any other 500mA fuse, or search Ebay for a 500 mA polyfuse.Edit: I thought you were talking about an UNO, but you are not. Anyway, a 500mA should be enough . (Normally a 250mA fuse will do the job also)
Oh it's just because i wanted to also use a fuse on USB to serial so i don't burn out my computer. Would be just fine with 500mA do you believe so? or maybe 250mA would be better?
Sorry John a poly fuse is not something that goes in a socket, it is soldered in.