In any case, a lot of the mouthguards are just bruxism / teeth grinding protection. I'll let you know that "pushing the jaw forward" is how my device works.
Other people have linked cheaper stuff from various places online which seem like they push the jaw forward. But most dental-guards I see at Target / CVS / etc. etc. are just bruxism protection, probably not designed for sleep apnea.
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Now that I know what I have and can do comparison shopping, the thing that has gotten good reviews seems to be "ZQuiet". Seems to be well reviewed by 3rd party websites, and not super-expensive. $80 or so. https://zquiet.com/
Another person upthread claims they got good results from something from Amazon, but I couldn't find much information about that company or website.
Also mouth guard don't cause choking hazard.
I had a dentist prescribed/adjusted MAD which cost $400. I hated that thing. I purchased a $10 nightguard at Target, less intrusive, smaller, more flimsy and flexible version, at target. It works great and last 6 months.