Thanks, XFWS and ungerman. I had asked the B&H Chat service for advice, but I'll try the link too. Taking off my glasses doesn't help very much because 1) I have to keep track of them, and there's usually too much going on already, 2) the eyepiece is still hard to reach, and 3) I need more correction than the diopter.
I have a set of binoculars that has neat extendable eyecups, so I searched the binocular and telescope discussions. There are many options, but they are all round. That led me to an extender on eBay that has adapters for a large number of SLR cameras. It is really inexpensive, so I might try it. I'd probably have to glue it on, but that's o.k. I also ran across recommendations to glue on O-rings.