The IMUSA pots are hit or miss at Walmart stores. Sometimes some stores have them, other times, they don't.
But keep in mind you can order one online and get free shipping to your nearest Walmart and just go pick it up. If it doesn't fit, you can return it to any Walmart. Just make sure you keep your receipt after you pick it up.
By the way, when I got mine at Walmart, I had the top and the bottom of my SJS with me.
I did get some looks but I tried the fit with 5 different IMUSA tamale pots.
First one fit okay. So I tried another, fit wasn't as good so I put it back in the box and replaced it on the shelf.
Then I tried the next one, and so on. I think it was the fourth one out of the 5 that fit the best so I bought it.