I was just reading through this thread and have the exact same issue for a site I built for a client (https://www.campshiloh.net). Their registrations opened up two days ago and are nearly sold out already, but it would be great to show inventory levels in the future when we open registrations again. Can someone provide me with the code to make this happen, please?
I have combed the internet for hours and found nothing, and don't feel comfortable writing Javascript on my own. 🙂 I did find a plugin that might help, but it looks like it was made for products (not services) and on 7.0.
Thanks in advance for your help!