Herb wrote:

Lights don't much care. As long as there are no heating elements,
electronic circuitry (like what's required for flickering lights or a
flickering fireplace, sequential lights, etc.), or motors. Make sure
that the actual voltage is enough to light the lights and not so much as
to burn them out.

You COULD, instead of finding 3v transformers, wire the lights in series
of 4 bulbs each and feed them standard 12v.

- Herb

Thanks! I'd thought to possibly go the "series" route, but I wanted to
route all of the 3v wiring to one central location supplied by a 3v AC
source. That would, I assume, drop the voltage far below the 3v I needed
(LOTS of lights). Then I thought of a "cheap" Variac, around $80 new for
around a 10 A output, that would need an isolation transformer to be
safe. THEN, I remembered an old variable, heavy DC Lionel train
transformer long lain in our cellar, and I actually FOUND IT among our
newly unmarried daughter's belongings :-) Seems to be good for 0 to
around 12v and 2.5A output. I need to find out whether it's fused
(internally). I can monitor the output amperage and use another 3v 800
ma DC transformer for additional lighting which I'm sure I'll need.

I asked the wife to, in the future, try to buy 12v lighting if at all
possible, easier to find power supplies for, including use of my 12v DC
power supply I use with my model aircraft battery chargers, if I can
find it among the disorder we call our home :-(