You don't need specifically a Packard Bell CRT, any CRT will work. Although for that system to keep with the times, you would want to track down at most a SVGA one not one of the new ones.
Reason you can't find them is that they are mostly in trash heaps since when they break there is 0 need to try to fix them, or even if working the cost of electricity to run them or space they take up or weight are all huge reasons to get rid of them. There is also pretty much 0 collect-ability value of old CRTs so there is no-one stocking them up to sell in 10 years. Even the iconic CRTs that start up a long line of models like the first NEC Multi-Sync are not really wanted unless you run a museum.