You might not have to get it repaired. The picture will be at its widest with no slug in the coil. So, remove all pieces of the broken slug, and see how the picture looks--it might be as wide as you need it, or just wide enough to be "acceptable" without paying someone to work on it.
In the past, I've broken pieces off of stubborn slugs before, and was able to remove them and reuse them by turning them upside-down (there's often a hex socket on both ends of the slug). This won't work if the fracture goes clear through the slug, but if the damage is just at the top near the hex socket, then this will definitely be a possibility. If you can't work the slug from the topside, you might be able to desolder the coil from the board, and turn the slug from the bottom.
If it doesn't turn with minimal force (you saw how fragile the ferrite is), be sure to heat all sides of the coil with a blow dryer for several minutes.
If you need to replace it, Bob Roberts lists the K7000 Width Coil at $10 (US Dollars).