TOUGH-TOX NATO ADAPTERS BLACK
Perfectly fits casio models: 
G8900-1  GA100-1A1  GA100-1A2  GA100-1A4  GA100C-1A3  GA100C-1A4  GA110-1A  GA110-1B  GA120-1A  GA200 GA120BB-1A  GA300-1A  GAC100-1A  GAC100-1A2  GD100-1A  GD100-1B  GDF100-1A  GDF100-1B  GDF100BB-1  GR8900-1  GR8900A-1  GW8900-1  GW8900A-1 DW5000 DW5200 DW5300 DW5600 DW5300CV DW6100 DW6200 DW6500 DW6900 G-2500 G-8900 Frogman Riseman Rangeman and many other Casios that feature 16mm lug width.  These adapters will fit models including:  DW5600/GW5600/GWM5600, ETC (Does NOT fit GX56) DW6600 DW6900/G6900/GW6900, ETC (Does NOT fit X6900) DW004 DW9000/DW9050/DW9051/DW9052 G2200 G2210 G7900  G8900 GA100/GA110/GD100/GA120/GD110/GLS100/GD120, ETC  G9100 GW9200 G9300 GW9400 Rangeman