Use the opportunity to get a new driver fitting. Just changing out your shaft will only get you back to where you were. If you do not have the budget for a new driver, just see your local golf repair shop to do a replacement.

Time for a fitting.

how old is the club? I was going to ask about warranty, but since you don't have the shaft, that's a moot point. Maybe you can research what the stock shaft offerings were when the club was released.

some of the box stores sell off their demo shafts.

On the other hand, with the price of many shafts, is it really worth it to buy a shaft vs. getting a new (or prior) model? Not trying to spend your money, but depending on the shaft, you could be spending a good portion of the price of a new club. And don't discount getting a used club from one of the stores where you can take some swings.

Finally, do you have a PGA pro that you see for lessons? If so, ask the pro and get fit for the replacement. It might cost a few extra $, but the end result will be worth it.

Steve