What about Officemax of Office depot?

Both can get it done for you. Staples can also get it done for you, and so
can your local Mom-and-Pop office supply. However, I would rather go
directly to the engraver.

If the aircraft is purely day VFR, or the placard is only for something like
the warning notice for an amateur built aircraft, then a trip to the local
engraver is probably all you'll ever need.

OTOH, there is an entire science in backlighted engraved panels. At the
time that I left the avionics business, the backlighted panels still all
used incandescent lamps--many of which were weed lights--and there was a
significant amount of work performed in replacing lamps and touching up
panels at annual on aircraft such as King Airs. At that time (circa 1986)
red or yellow LEDs were cheap, green cost money, blue was expensive, and
white did not exist. Today, white leds are quite affordable by aircraft
standards, draw little power and run cold, and are far more reliable than
incandescents--so there could be an interesting project in back lighted
panels. Alternatively, if the aircraft is to fly at night or during civil
twilight, at least make the labels oversize--because switches and breakers
are frequently a long distance (and shallow angle) below the "eyebrow"
lights.

Peter