Barton Watch Bands sells black PVD stainless steel strap adapters for G-Shock 5600 watches (and other models) that are compatible with 22mm quick-release bands. The $13.50 adapter set also includes two 22mm spring bars to attach bands that do not have quick-release bars.
Barton also offers several lines of G-Shock-compatible bands that include the strap adapters. These bands include the Elite Silicone and Crafted Canvas (both quick-release), along with the Elite Nylon NATO Style, Leather & Rubber Hybrid, and Cordura Fabric & Silicone Hybrid. The Elite Silicone and Crafted Canvas bands are also available in a long size, with the standard size fitting wrists 5″ to 8″ and the long size fitting 7″ to 9″.
According to Barton, the strap adapters are compatible with the following G-Shock models: DW-6500, GW-B5600, GB-5600, GWX-5600, DW-5025, G-5600E, GW-M5600, GLX-5600, GLS-5600, GW-M5630, GW-S5600, DW-D5600, DW-5000, DW-5035, GW-5000, DW-5030, DW-5600C, GW-5600J, GA-100/110/120, GD-100/110/120, GA400-700, GX-56BB, GWX-56.
International shipping is available.
(Note: The spring bars can be difficult to remove and install on a G-Shock, and those who are lacking a spring bar tool or are not mechanically inclined may want to think twice about it. Several user reviews have stated that the Barton adapters are a very tight fit and are difficult to install. Also, aftermarket parts are not guaranteed to work as well or to be as durable as official parts.)
BartonWatchBands.com:
Watch Adapters for G-Shock | G-Shock Compatible Band Sets with Adapters | More 22mm Bands
Some Barton bands are also available on Amazon, but the adapters and G-Shock sets are only available at the Barton site.
Barton Watch Bands Storefront on Amazon.com (affiliate link)
Reading the comments on the Barton site it seems like the Jaysandkays adapters are still the better choice as they are much easier to install then the Barton ones.
Yeah that might be the better option. JaysAndKays also has adapters for the GA-2100 and more.
JaysAndKays (affiliate link): https://www.ebay.com/str/jaysandkays?mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5337710300&toolid=11800&mkevt=1
I can confirm this. I bought some Barton ones as soon as they came out and they aren’t that great. The first time I bought some they sent me me the NATO but no adapters. Took them weeks to finally get me adapters. Compared to the Jaysandkays they are incredibly (to almost impossible) hard to install and the springbars they supply are very low quality – I didn’t trust them as they would come undone if you yanked on the strap. Also from what I remember you also cannot use the stock Casio springbars with their adapters. I ended up never using them and went back to my JaKs
https://www.reddit.com/r/gshock/comments/sz4e7o/comparison_between_barton_and_jk_adapters/