There is plenty to listen to in Nassau and Suffolk Counties without a trunk scanner. Your first stop should be the Radio Reference Database.
All Fire Department activities with the exception of Fire Marshal and HazMat dispatches for both counties are conventional.
Nassau County PD is on their P25 system, but the simulcast is still active for the UHF frequencies.
There is still plenty of activity on MTA Police, and LIRR Frequencies for you to hear.
NYS Police are conventional, and operate on a duplex system (1 frequency is for Base to Mobile, and another is Mobile back to Base)
The US Coast Guard is busy this time of year. Make sure you listen to them. While you are at it, put in the Coast Guard Aux.
Depending on where you are, you may be able to hear FDNY and NYPD. Maybe you can also pickup Westchester and some of CT.
While most of my scanners are trunk scanners, I still have my fair share of "Conventional Only" radios that I use daily. There is plenty to hear.
And even though your PRO-97 won't do the Rebanded Motorola, it will still do rebanded EDACS.