The C7(b9) belongs to the category of altered dominant 7th chords (general: V7alt). That are dominant 7th chords with one or more of the altered tensions b9, #9, b13 or #11, in which #11 has a special role. Please look up at the description for the 7(#11) chord type. Altered tensions mainly occur, when the V7 chord resolves from V to I, like from the C7 to Fmaj7 or Fm7. The very common abbreviation „alt“ lets the player decide which tensions he/she wants to use (the versatile guitar player will always decide by himself anyway…).
The b9 is located a minor 2nd above a root tone, but will always be written as b9 and never ever as b2 (the 2 only occurs in sus2 chords).
A C7(b9) has the notes C (1), E (3), G (5), Bb (7) and Db (b9). While the 5th will often be omitted when using other altered tensions like #11 or b13, it is normally part of the game in a 7(b9) chord.
If you don't play the root C, the remaining tones form a Edim7 chord. Since dim7 chords consist of only minor 3rds, they are completely symmetric and therefore Edim7 is the same chord as Gdim7, Bbdim7 and Dbdim7. They all have the same chord tones!
That means you can replace a C7(b9) oder add to it a Edim7, Gdim7, Bbdim7 ond Dbdim7 chord. Just take one of those dim7 chords and move it up or down by 3 frets to the next one. That of course works even better if a bass player provides the low root C.