Yes. How many ways do we have to say it? I even posted a link to a two page thread that goes into explicit detail about why. There is no such thing as a 9" Color CRT which will fit within the dimensions of a pre-Color Classic compact. Period.
And yes there are all kinds of hacks where PowerBooks or G4 Cubes which run OS 8 or 9, can be put into a compact case. Go with a Grayscale CRT and you'll be fine. Otherwise, if you absolutely have to have color without modifying the case, you'll have to go LCD. There are numerous threads in this forum that discuss many such hacks, with some excellent pictures. Browse around some of these old threads and you'll find a lot of good info.