I have weight gaining issues to:

I looked up what drugs don't need step therapy or prior authorization through BCBSM here . I then cross reference them with weight neutral drugs. Here's your list:

Risperdal pg. 33
Geodon

Lithium pg 39
lamictal
topamax

cymbalta pg. 32
Wellbutrin, SR
prozac
Zoloft

If your doctor will not try weight neutral get a new one. Mono-therapy is ABilify but it requires step therapy.