Monitor deflection magnets; what to do when one falls out & breaks?

Hi, I have an old B&W "specialty" monitor which recently stopped working. In the process of moving it around (to/from repair place) I noticed a little black "tube magnet" dropping out when I took the cover off. At the time I didn't think much of it (those in the know can chuckle now). So, after a bout of replacing bad caps with no luck, I eventually broke down and replaced the deflection board and the monitor sprang to life. Much joy. (note: "specialty" = designed for a specific computer with a special ECL video connection and has no standard connector or interface. and no schematics) So, monitor is working. I proceed to adjust the H & V size, linearity, etc... I notice that the bottom and sides will square up nicely but the top edge has a large "dip" in the middle. No amount of trimmer fiddling will fix this. light goes off. "found" tube magnet is part of yoke assembly. So, I notice where the missing magnet came from. Naturally it's on the top side of the yoke assembly. But - the "tube" has broken into 3 pieces (it was broke when I found it. honest). I carefully glued it back together (no glue in the joints, however) and replaced it. This helped a little but did not cure the problem. [note to reader: I never took that fields course. I know nothing of magnets.] So, - is a broken magnet pushed back together not as good as a whole magnet? (strength wise) - can I get a new magnet somewhere? - is there anything special about these magnets? - do normal monitor repair guys just have a box of these laying around? - does this sort of thing happen all the time? -brad