Temperature controlled work surface? I made croissants yesterday, but couldn't be bothered to keep returning the pastry to the fridge in order to keep it cool, so the butter became too soft.

While the end result was still pretty amazing, I couldn't include enough butter to get the right crumbly texture.

One alternative to returning the dough to the fridge would be to have a temperature-controlled work surface.

Does that exist, or will I have to make my own?

It ought to be fairly simple to slap some peltier elements onto a slab of aluminium or stainless steel, and a small PID controller.
(It would probably be easier to work on stone, though, so one could glue a piece of decorative marble on top. There may be problems with thermal expansion, but you can get tiles made for underfloor heating, which ought to work.)

It would also be possible to reverse-bias the peltier elements to heat up the work surface slightly, e.g. in order to let the dough rise.

Has anyone made such a thing as a DIY project, or can they be bought ready-made?
You can search online kitchen suppliers for marble slabs used for this purpose. You can either take advantage of the thermal mass of the slab warming up more slowly, or if you have refrigerator space, you can even pre chill it before use.

I don't include links because they can become stale, but searching just now finds several. Search for "marble pastry board"