What are my options for saline lip injections (temporary)?

Saline can be injected into the lips to give temporary fullness.  This most likely would not last more than a few days.  You could consult with a facial plastic surgeon, plastic surgeon or dermatologist to see it they would be willing to treat you.  

Saline can be injected into the lips as a very temporary test for lip augmentation. In my experience it will not last more than about 8 hours.

I'm unsure why you want to do this as it would only last for a few days, max......??"This answer has been solicited without seeing this patient and cannot be held as true medical advice, but only opinion. Seek in-person treatment with a trained medical professional for appropriate care."