I've had that problem before too with the anal electrode falling out. Depending on the electrode you are using up your ass you might be able to do what I've done. I put my belt around my waist and then on two of mine I was able to secure twine to them, like on a drapery cord. Then, I tied one cord to the front of my belt, and the other to the back of my belt. It really held the electrode up there and allowed me to do some excellent ghost fucking with a bipolar electrode.
I also use a P.E.S. prostate ball, the other electrode then on the head of my dick, and using Zeus Gel. I lie on my back with my knees up, the P.E.S. prostate ball up my ass and it hasn't fallen out on me, yet, but I'm really careful about that. If you get it just right, the metal ball will start pumping in and out some, kinda up and down inside you, and also your dick will bounce some. I'm not into pain or anything, just a feel good time, and I always have HFO's.
Using the same setup sometimes it's fun to sit on the toilet. I put the lid down, a nice thick towel on the lid, and then a plastic bag on top of the towel. That way, nothing is going to fall out of your ass. Sometimes I also tension myself like trying to have a BM, you can get some interesting sensations like that. I always do a HFO that way.
There are all types of anal probes, so there's lot to choose from. Some work well, others don't. Zity Biz is an incredible forum, I love it. Sometimes I also go to http://smartstim.com/ they have some good advice on plugs, etc.