This tutorial is a relatively short one, useful for any G-Shock watches that have a 2 piece wristband that uses specialized strap holders. These are holders that attach the strap pieces to the casing, unlike the strap adapters that allow a single piece wristband (NATO/Zulu style) to be attached.
The most prominent candidate for this conversion is the GLide GL-110. This particular model came on a beautifully designed and comfortable brushed twill cloth/nylon Velcro strap. Unfortunately, the strap was not designed to be very durable and hold up well to the rigors of aggressive use, such as swimming in salt water.
Here is an example of what one strap looked like on the GL-110TC after a few years of use:
The strap end pieces are made of plastic and rubber and are secured to the straps with a thick snap-in pin. At first glance it looks like this is fused into the end piece, but pressing firmly on the small end of the pin will dislodge it. You can then extract the strap from the end piece, like so:
If you buy a replacement 2-piece strap, it will need to be at least 22m in width (although you can use 24mm and slightly trim it width-wise) and a good thickness so that it fits snug inside the end piece. The edge with the loop in it also needs to be firm, to hold up to the tension. You can see in the photo above how there is a shorter black segment sticking out that acts as the loop. It is made from a very tightly woven nylon material and is quite stiff.
I bought a 2-piece Zulu strap for a suitable replacement. I then trimmed the ends to recreate the loop, that slides inside the end piece. The trimming is best done with a Dremel, although you may be able to cut it with very sharp scissors or a knife. After trimming, use a lighter to cauterize the ends--this prevents fraying.
Here's what the watch looks like when it has a nice condition original strap attached:
Here's the watch with the replacement strap:
(Note: I didn't fully adjust the band here, so the pin is sticking up a little; it otherwise rests flush to the buckle)
The replacement strap was initially stiff, but softened up quite a bit from the warmth of my wrist. It now fits very well and feels almost as comfortable as the original. Doing this allows the preservation of the original strap, letting the new strap take all the abuse and survive it better. The total time it took to do this modification was basically 30 minutes, from start to finish. I had also done the strap adapter option, which required trimming the adapters and then inserting an appropriate single piece strap. This works, but unfortunately the watch sits up a little higher, because the strap raises up the casing. The two piece strap feels more comfortable and stays in place better.