I also have 4 pair of these showing up from Amazon today since they were only thing available when I ordered a few days ago (even the $50 ones were sold out at the time): https://www.amazon.com/gp/product/B06XTL5M5T/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
According to the Q&A they should fit adults too but I can let you know for sure when they arrive here in next couple hours if they actually fit. If you want a pair or two just let me know, offer still stands.
Unfortunately only snagged 2 pair at Frys so don't have any extras of the one size fits all version.
Edit: Yeah these "kids" ones fit just fine.
Just make sure they're not knockoffs. I've read there are bad ones out there that are selling pretty cheap. I ended up getting 4 pairs on Amazon for $20. But, they're from the manufacturer that NASA recommends (https://eclipse.aas.org/resources/solar-filters)
Here are the ones I bought:
4-Pack Premium ISO and CE Certified Lunt Solar Kid Size Eclipse Viewing Glasses https://www.amazon.com/dp/B06XTL5M5T/ref=cm_sw_r_cp_apip_n8zvg9JP66AiE
I'm also making pinhole boxes with the kiddos.
Stay safe!