The Australian distributor said they had the black ones as a spare part,
If not in Australia you could check with your countries Ricoh agent and see if they will get them.
p/n L7531023 FRONT RING CAP, AU$20 posted within Australia.
Just a correction on this, L7531023 seems to be the part number for the III / IV ring
I think the GR ring is L7661023
| Ricoh GRD I Limited | Ricoh GRD II | Ricoh GRD III | Ricoh GRD IV | Ricoh GR | and some inspiration