https://www.amazon.co.uk/Scruffs-BED-RCD-934613-Cool/dp/B00VTTO0RK
This looks like what I bought, but I didn't buy it from Amazon. I guess you could call it a mat.
I don't think it was meant to be frozen, but it works. I have had to replace two because of a hole, but nothing with massive leaks.
In the beginning, I put a sheet over it, to avoid the dog being directly on ice, but eventually, he used it without the sheet.
When the weather was too hot, he would be on the mat, in front of a fan, and not move until it had melted. Then he would expect it to be replaced.
Spoiled dog...
We had a thread here a while ago.
https://www.amazon.co.uk/Scruffs-BED-RCD-934613-Cool/dp/B00VTTO0RK
Get a Scruffs mat, put it in the freezer. When frozen, put it on the floor in front of a fan. Forget walks, except for early morning and late night.
I had to get several mats. When one wasn't cool enough, he demanded a new one.
While my Sammy loved his ice mat, it took some getting used to before he understood the purpose.