7H:
I've experimented with the electrical tape idea, and variants, and it works, but not real practical if you are CCing. I'm a progressive eyeglasses guy myself. Yeah, the glasses can help you see the sights, but the target is even more fuzzy. I've found the best solution to be Crimson Trace grips. Of course, they're not available for all models, so you have to be selective.
Last fall I took a deer with an open sighted flintlock. Early morning, he was just back in a treeline. Poor light. I could see the sights, and no deer, or see the deer, but no sights. Deer have wondderful camoflage in a dimly lit woods! Probably took me 8 or 10 minutes to get a shot where I could see the deer and the sights with any certainty. The next day I bought an in-line with a nice scope for hunting. I still shoot the flinter, but only at well-lit paper.
I think this is what it boils down to for me: When it really counts, use a sighting system that will work for old eyes, i.e. Crimson Trace or a scope. For fun at the range, try other stuff.
Good luck!
RBH