I don't take Prozac, but I have had trouble with some other generic drugs. and I've been able to switch.
Can you find out the manufacturers who made the switches? Are there any generic companies still using the old formula? My small pharmacy will get me a different brand of generic if I ask.
You may have to go so far as to contact the manufacturers - or possibly get a friendly, helpful pharmacist who knows you to help you do the research. Pharmacists have lots of manufacturers they can order from, usually go with the cheapest so their profit is higher, but if you have a problem they are often willing to order things specifically for you.
If you have to go to a hospital make sure to take your own meds with you. Hospitals often give you whatever they want to, but your doc can write an order for you to take your own meds.