Why not just move closer?
I reeeeeeally don't think the RSO would like that.
seriously, try a peep sight. it changes how your eye works. almost like a magnifying lens. I think they make some with screw-in aperatures so you can try different ones. if a regular aperature won't do it try smaller and smaller. the down side is that it makes the sight picture darker and darker. but, even the smallest one is no problem on a bright sunny day.
before spending money you can try it out by poking a pinhole in something. (pinhole, nail hole, different sizes) hold a pencil at arm's length, look at an object 100 yards away.
you can try it right now if you want to see the effect. poke a small nail hole in a piece of paper (3/16" or so) and hold it 1-3" from your eyeball. objects 2 feet to (infinity) are now in focus.
also, they have one that has an actual lens in it just for people with vision problems. or, try 1.25 or 1.50 reading glasses.
targets. take a blank sheet of paper and draw a crosshair on it with a black magic marker. then fuzz it out so the lines are 1/2" or" 3/4" thick. you can leave a blank spot in the center if you want to. I can't see a thin black line at 100 yards either, that's what I do.