I made up a kit myself using hi spec discs and bells, mainly to make sure I can get discs in future. They charge £130 for a pair of plain discs or £190 for drilled or grooved ones in 288 and 295 x 26mm. However as Keri says the discs will need to match your current bells - the godspeed bells probably can't be fitted to hi spec discs (or ap discs or compspeed etc etc). If you need to change the bells too you need to make sure you get them in the correct offset as well, not exactly straightforward unfortunately.