I haven't heard of anything like that, and I'm not sure what they would do exactly anyway.
Because vacuum tubes work in a vacuum, essentially all of the cooling of the actual tube innards has to be by radiation - you can cool the glass, but I don't think glass failure is much of a worry.
My guess is your real concern is keeping the overall unit cool enough, so I would would think about putting a small quite box fan behind the unit to ensure you've got some air circulating. If the chassis is cool enough, you should be good.
I would look at NewEgg for a case fan. They are 12VDC - you've probably got an old 12VDC wall wart or laptop PS sitting around that's more than ample to power it. The only trick is how to make it inconspicuous. You don't need to move much air at all, just enough to compensate for the cramped quarters. The primary concern is to get a really quiet fan.
Because vacuum tubes work in a vacuum, essentially all of the cooling of the actual tube innards has to be by radiation - you can cool the glass, but I don't think glass failure is much of a worry.
My guess is your real concern is keeping the overall unit cool enough, so I would would think about putting a small quite box fan behind the unit to ensure you've got some air circulating. If the chassis is cool enough, you should be good.
I would look at NewEgg for a case fan. They are 12VDC - you've probably got an old 12VDC wall wart or laptop PS sitting around that's more than ample to power it. The only trick is how to make it inconspicuous. You don't need to move much air at all, just enough to compensate for the cramped quarters. The primary concern is to get a really quiet fan.