Hi there,  having tried the slow cooking pot or crock pot, I found
a much more favorable substitute for my glue pot is an electric fondue
pot.  I find them new at several electronic stores for nominal amounts,
with thermostat control ranging from 80 to 170 degrees F.  Setting it
to the lowest setting kept a water bath at perfect temperature; the
water was warmed up quickly and the hysteresis was relatively small.

Baby bottle warmers: make sure that they stay on before you buy one.
I bought one and it came to temperature and then, like a coffee pot,
it automatically shut off.  Completely worthless!

Crock pot: excellent but it took a long time to come to temperature.
To make this practical, I boiled water in my electric kettle, mixed it
with half tepid water and then put it in my crock pot, finally adding
my jar of hot glue.

Regular stove: easiest to use for a quick warm up for a quick repair,
but no good for a long period.

Regards,

Eli Shahar
Sonora, California