I also need extra counterweights for my iEXOS-100 so I've been checking the ES website monthly since I purchased the mount (Dec, 2019) but have yet to see the black counterweights in stock. It is possible I might have missed them being in stock for a week or two one time or another but they have yet to be in stock when I'm looking to part with my money. I'm not sure what I'm going to do. I want to keep the weights tight against the counterweight shaft just like the original counterweights so I don't want larger ones but I might need to opt for an alternative or compromise. I could paint my CG-2 counterweights black and use them, I suppose. I rarely use that mount.
I like my counterweights to be completely secured to the counterweight shaft... each weight secured from all movement. I don't like them being able to spin or even move a hair so adapting exercise weights are out of the question for me. I do, however, use some chrome exercise counterweights for a homemade pipe mount I made but that is a manual mount and not used for astrophotography.
I could also use an extra counterweight for my EXOS2-GT too but, at the moment, I don't want to throw any more money into that mount since it isn't the PMC-8 version so I might be significantly upgrading that mount in the next year or two to a Losmandy G11 or similar.
Explore Scientific iEXOS-100 and EXOS-2GT (non-PMC)
Explore Scientific ED 102mm Refractor