There are several types of proving boxes for sale on the internet, they are very variable in price.
This one on Amazon is £15.00 with free delivery
Amazon serial no B0C7ZPSFHK
Probably couldn’t do better than that. I think I’ll get one ordered for myself.
Let me know if you get one and I’ll show you how to use it to make a sourdough starter and then bake your own sourdough bread.
I’ll review it when I’ve received and tested it.