Have you tried a FC2 (female condom)?
http://www.fc2femalecondom.com/
I first tried it because I was trying to find a solution for those men who comment on discomfort or desensitization with male condoms. Well, it turns out that all most all of the partners I have tried it with love them. I use them about 95% of the time and a great bonus is that I prefer them as well.
Also, once the FC2 are in for a short bit, they warm up to the same temperature so they are the closest you can get without having to endanger your life or anyone else that they are with.
They are a bit expensive, but I feel it is totally worth it.
With cock rings, I use these
http://www.amazon.com/Vibrating-Sili...one+cock+rings
They are stretchy and have a vibe thing on top for me
I use new ones for each person. They might have a bit too much stretch to them for you????
You'd possibly would want to look into one that can be sanitized. A friend of mine uses a fake leather one with Velcro and uses sexual toy sanitizer to clean it.