Voltage halver.

A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.

Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.

Rather than limit the adjustment to 6 V, I think of halving the
output.  An integrated circuit in a 4 port package is conceivable.
https://www.youtube.com/watch?v=VJfqBQ2ybpk

Does the marketplace offer a solution?
Another idea?

Thanks,                  ... P.