I would recommend the Holy Trainer. While it is quite expensive, it has a perfect fit and is extremely comfortable to wear. I sometimes forget I am wearing it. Once I needed to get out of it badly, because it wasn't sitting right with my ball. I managed to get my cock out, but I could not get the thing off and had to call my girlfriend who has the key.
It is a pity that your wife don't want to play, but perhaps you went too far too fast? In my experience, suggesting a threesome (after some pillow talk and fantasy play), was what made my girlfriend go for it. From threesome it is not far to cuckold and from there chastity. Good luck!
