Naughty Boy! If you've still got the ferrite slug (and you should have), you can adjust it by sliding it in & out (possibly holding it temporarily in place with blu-tac) then use your soldering iron (pref on a low temp) to put a few drops of wax round it to fix it more permanently.
Your best bet is to find one from a junker or try to rebuild the one you have. Width coils are generally paired with the FBT and yoke. The chances of you finding a new one are pretty slim. Figure out how many windings, the wire size and the pinout and try to go from there.
It might be that you could use an Electrohome G07 coil as a replacement. They're pretty plentiful. Alternatively, you use one as a basis for rewinding job.
Per the ADM-3A service manual (I have a PDF if you'd like a copy), that's 'L101', a Ball Brothers PN 1-016-0303. Check with these folks for replacement: http://www.dotronix.com/pages/productList.php