I use them about 75% of the time.
You can get them direct from manufacturer for about $50 for a pack of 24.
Depending on the gent, it can be more trouble than its worth. If they are very adventurous, like to change positons a lot, ect. It tends to get in the way, and you spend more time than necessary fishing it out, and making sure they stay inside the condom. It ends up being a waste of a $3 condom.
However, I find they are perfect for the gents whos "home lifestyle" has him unaccustomed to wearing condoms at all. You get the protection and he has uninhibited sensation.