The problem with this scenario is that anyone who deliberately set out to shoot down that aircraft wouldn’t have done it so far east when the aircraft would have been flying very high overhead. Someone looking to do this would certainly have positioned themselves further west — closer to JFK Airport where the aircraft departed — since the altitude would have been much lower.
The problem with that scenario is getting caught. Further to the east is safer for the perpetrators.
Several years ago I read some of Jack Cashill's work on this issue, and he seemingly identifies what sort of missile was fired at the aircraft.
If you have the resources of a wealthy Iranian family, you can get access to weapons that are not readily available to your ordinary run of the mill terrorist.