Gotta make your own. Using the core of most any rope will do the trick. The rope tangles in their teeth.
You can pop the fist out in under a minute with care. Obviously if you have no care for the fish you can do some serious damage if not removed properly. Those of us on this board (I presume) do have care for the fish, which will ensure their survival. In all honesty, I've had the most problems with releasing fish when they've burried the lure down their throat or into their gills. Now I'm not sure how much oxygen these gar breathe, but they've been the most resiliant out of water species that I've encountered.
I have had some awful tangles, but never felt like the fish wouldn't make it once released -- they've always kicked away hard. I'm sure most others with experience would agree. Also -- by limiting the length of your rope fly you also limit the amount of tangle possible.
So yes, there is potential to harm the fish while using rope flies, but with care I personally haven't seen the harm.