OEM radio

So when I bought my new integra guy gave me a OEM radio. I thought cool…boy what a headache. So I’ve been reading to find a code but from my understanding you need the Vin of the car and serial of the radio and then you can use hondas code database. That’s fine but my car is a 90 anD the radio is made in 98 obviously not the original. I can try it when the hours of a website are open. Ive also read go to the dealer but it seems 50/50 If they will give it to me or not. I’m going to call on Monday but is there anything I could try before then?