Ricoh GR III with GW-4 Wide Conversion Lens, GA-1 Lens Adapter, and 64GB SD Card - Walmart.com
Amazon.com : JJC AR-GR3 Lens Filter Adapter Replaces Ricoh GA-1 for Ricoh GR III GRIII GR3 Digital Camera with GW-4 Wide Conversion Lens or 49mm Filter : Electronics
Ricoh/Pentax Ricoh Wide Conversion Lens GW-4 for Ricoh GR III
Ricoh GW-4 21mm Wide-Angle Conversion Lens for Ricoh GR III Review
You can use the Ricoh GW-3 21mm wide-angle conversion lens on the Leica Q camera - Leica Rumors
Ricoh GW-4 Wide Angle Lens Review for Ricoh GR III (GA-1 Review) - YouTube
21mm Ultra-Wide Angle Review for Ricoh GR III (3) - ERIC KIM