Okay, I‘m an older diver, and in the 1960s we made our own gloves. Some have mentioned taking a glove to a local taylor and have them sew the thumb part shut. Well, sewing the nylon on a neoprene wet suit or glove is not something these commercial taylors can do, as the sewing on a wet suit must not penetrate through the whole material. Why? Because that leaves little holes in the material, which will pump cold water in and out of the glove. It will be really cold.
Get some 5mm wet suit material (sheet), put your hand down on it and draw an outline of your hand, allowing about half an inch of extra material on the fingers, and maybe a bit more for the hand (maybe an inch). A little-known secret of our old-style cold water gloves, which we made of then 1/8 inch sheet neoprene, is that you don’t need to separate all the fingers. The thumb (which here would be left out) and first finger were outlined alone, and the last three fingers were combined for a much warmer glove (you use the last three fingers together anyway for almost everything). You need to make a mirror image of this for the other side of the glove.
Take the neoprene cement, and coat the surfaces with the neoprene (the edges). Let that first coat dry completely. It usually takes over ten minutes. That way, you have a closed surface to coat the second coat onto. Do coat the second coat, and let it dry until tacky. Then simply press the two edges together. let the glove dry overnight, and you have it. It’s actually pretty easy to do.
Now, if you can find it, use neoprene coated with nylon on only one side. You then have more surface for the neoprene cement. It will be easier to get on and off if the neoprene is on the inside, but will be tougher for barnacles and other sharp things if the neoprene is on the outside. Or, simply use two-sided neoprene, and not worry about which side it is. It will probably hold up well.
Since these gloves are simply cemented together, you may have to do some repairs occasionally, as seams do split sometimes. But that‘s pretty easy with completely dry neoprene. Simply re-glue it using the same technique as explained above.
SeaRat