I got mine in person from a large furniture moving company somewhere in South Los Angeles. But I did find serviceable blankets from Harbor Freight.
https://www.harborfreight.com/72-inch-x-80-inch-movers-blanket-66537.html?_br_psugg_q=moving+blanket
I think anything in that range should work. The object is to make a box with no gaps on the sides and be made out of a material that you can’t move off the table with your breath or a light breeze.
I may go back and change that formula since nobody seems to be able to find the heavier blankets. 6 lbs to 8 lbs seems to be the available sweet spot.
I probably worked a little too hard at the design because I actually cut the pipes to fit (all one size), but I didn’t have to. I found a display case in Home Depot that will sell me 24-inch long plastic pipes precut. Finish off with four corners and four end caps. No glue. There are no stress points and you can knock it apart for storage when you’re done.
If you use the longer pipes, you just have to be careful to lay the top blanket the right direction so it meets the table covering on all three sides. With the 20-in pipes I intentionally cut, you could place the top blanket any which way and it would always fit.
The Kitchen Table Sound Studio is the junior version. I’ve traveled with a full stand-up blanket studio.
The walls are hung double (third pix up). They’re remarkably effective in keeping casual noises out and they just kill echoes. It’s not a fully soundproofed room, but come back in 40 minutes and I’ll have the studio ready.
Koz