Wemoto, a English aftermarkes supplier, have Kyoto disks for the R100GS for less than half the price anyone else sells disks for.
I fitted one recently.
They work better with Vesrah pads than EBC HH pads did with the OEM disk, best Ive had.
And the combination was 25% the cost of a new EBC disc/pad set up here in Oz .
Kyoto are OEM equipment manufacturers in Japan so quality shouldnt be an issue.
Adelaide Hills, Australia. 93 R100 GS, 77 R75/7 ,70 BSA B44VS, , 86 R80 G/S PD, 95 BMW Funduro F650 ST