Amazon.com: Casio Men's G XL Series Quartz Watch Strap, WR Shock Resistant Resin Color: Black and Blue (Model: GA-100-1A2CR) : Clothing, Shoes & Jewelry
User manual Casio G-Shock GA-400 (English - 6 pages)
GShock GA 100 - Detailed How to Tutorial on Module 5081 - YouTube
G Shock GA 100 (module 5081) User manual and a VERY detailed functions overview - YouTube