Banding a tube, possible?

[ieure]

I have a Motorola XM-501 open-frame monitor in one of my 1970s B&W arcade games. It has a 20WP4 tube in it, with significant phosphor burn.

I have a 19XP4 tube which came out of an Admiral set which got junked, and was hoping I could install it to get a fresh display. Problem is, the 19XP4 doesn't have a tension band, so I can't mount it directly in the frame of the Motorola monitor. And, now that I think about it, it's an inch smaller.

So, question is, is it possible to install a tension band on a tube which didn't originally have one? Or do I need to keep looking for a donor tube?