I'm not familiar with that helicopter very well but I did a bit of checking. You didn't specify what belt, so I didn't know if you were talking about a belt that goes through the boom, like my Align 500, or if you were talking about a drive belt. Regardless, I did some checking. I looked at A Main Hobbies, they are either out of belts for the Raptor 50 or they don't carry them. I checked Heli Direct, their website is still down for maintenance. I checked ExperienceRC, they have a drive belt for $30. If that's the belt you are referring to, I would surely just go ahead and replace it. Just like on your vehicle, belts stretch, wear out, and dry rot.
Here is the link to ExperienceRC:
AK0089 Tail Drive Belt R30
Now, I did see that it says "R30" in the part number. That may be for a Raptor 30, I honestly don't know.
Regardless...I would get a new belt.