Individual Cosigners- Roommate Situation

[LBB]

Hey, looking for some help or to be pointed in the right direction on this board.

I'm looking to sign a new lease with 2 roommates in Brooklyn. Here's the catch- we need a cosigner and and 2 of the individual roommates have someone willing to cosign. HOWEVER, both cosigners are only interested in cosigning for 1 tenant's share of the rent/agreement.

Is it possible for a cosigner to specify which individual they are cosigning for and not be responsible for the entire amount?

Thanks in advance.

-lbb