Iris, you might want to take a low cost/low tech approach to see whether a
"formal" proof box will make enough difference to be worth the research &
investment. I've been baking bread for many years (soon I'll be able to
say many decades!) and have never found the need. But I've been blessed to
live in fairly modern accommodations which are toasty and not drafty.
The purpose of the box is to maintain even temperature & humidity around
your loaves as they are in their final rise. Consider taking a regular,
corrogated-cardboard carton big enough to surround your usual batch of
loaves -- maybe cover it with shelf-liner or the plastic material on a
roll, with release paper off the back -- pull off the release paper and
then you can stick it on a surface...like your box! ... and make it
decorative and easy to wipe. While you'll have to estimate when to peek,
this would protect the loaves as described and give you a chance to see how
much difference you experience.
If you love the results, you could look in bakery-supply outlets, often the
clear plastic lids used to keep the rolls & pastries fresh are often high
enough to do this job. Maybe your local bakery could include a lid for you
in their next supply order!