[old_tv_nut]

Manual degaussing coils all run on mains.
Unfortunately, a quick search on ebay now shows only vintage degaussing coils at prices around $70 or some small plastic wands that I have never seen before, that look like they might not be very effective. The small, less epensive circular coils I have seen in the past don't appear to be available.

Substitutes:
If you have a soldering gun, the large transformer in the body probably produces a strong enough field to do the job. Hold the gun parallel to the tube face, move it in circles across the face for a few seconds, and gradually move away before turning it off.
If you have a hand-held bulk tape eraser, it can be used too.