There's an app called reprovision that can do the signing on device. (it also needs to sign itself, so that uses up one of your free slots) IIRC, when I used it

There's an app called reprovision that can do the signing on device. (it also needs to sign itself, so that uses up one of your free slots) IIRC, when I used it any icloud login worked for signing, not just the one tied to the phone.