Aside from modifying the gloves yourself (if that's too complicated for some reason), find a pair of dive-gloves you like and call local tailors, to ask if they're comfortable working with neoprene.
This modification doesn't sound too bad. If I was going to do it myself, depending on thickness, I'd just flip cut the excess material, leaving up to an inch, flip the glove inside out, and use a sewing-machine to sew a line. Having tailored plenty of t-shirts, I would advise you to start leaving more material and space than you need on your first-line and checking the fit. Hopefully it's too loose. Next, sew a 2nd line slightly smaller, and check fit again. When you do finally get a good fit, you can feel free to cut excess cloth.
It's all too easy to make a mistake of making your first line such that the gloves are too small, which then means you have to use a seam-ripper which kinda sucks to use, and may damage the fabric.