Chuck, you don't need a two-stage pump. Any motor driven pump capable
of achieving 1-5-mm Hg of vacuum should do the trick. You don't need to
pump down to the micron region.

An important thing to note is that most lightbulbs are not evacuated --
they contain low pressure argon so that the filament material doesn't
evaporate as it would under a high-vacuum.

For a simple demo experiement using a bell jar, I'd pump the bell jar
down to about 30-mm of Hg, then turn on the current to the filament. It
will start to glow, then as you pump more air out of the jar it will
being to glow brighter and brighter, since less and less of the input
energy is being lost to air molecules. Of course you will need to use a
filament material that is (1) not readily oxidized and (2) has a very
high melting temperature.

This is the principle upon which thermocouple vacuum gauges operate.

For such a simple demonstration, I really don't believe that it would
be beneficial to get into issues like the rarified argon backfill,
unless of course you want a bulb that will burn for hundreds to
thousands of hours.

Harry C.