Here's my head:
https://www.amazon.com/Reliance-Prod...dp/B000FIDZLI/
I've been using it for years. It uses a ziplock bag inside, which I just toss in the harbor dumpster.
Offshore, I skip the bag (it's plastic) and empty the bucket
overboard.
If the ladies don't like it, I recommend "direct deposit" at the shrouds. (Yeah, I'm brutal.)
Properly sealed with its lid, it won't dump its contents in a knockdown, unlike some other porta potties.
My 1963 boat had no
holding tank - just a direct dump to the sea. Since I'm a licensed master I can't plead ignorance of the law, and the CG would throw the book at me. So I had the old head removed and the throughhulls sealed (throughhulls are evil anyway - my boat now has only three). The CG is fine with my "portable" head. It was a little
funny when I got boarded once and had to warn them not to "stick their hand down in there." I've considered putting a "biohazard" warning on it for the next time I get boarded, in case I'm not looking when they go to inspect it.
On other boats I've skippered, I've found that about half the underway
maintenance effort was devoted to fixing the heads, and many of the boat cabins reeked of hydrogen sulfide (rotten eggs) because of the challenges of sealing the
holding tank. I avoid all those issues with my maintenance-free head.
H2S by the way, is considered "immediately dangerous to life and health" at 100
parts per million (about twice the concentration where you can first smell it) and lethal at 500
parts per million. Just a whiff of it goes a long way toward inducing seasickness.