When a customer purchases a discounted package of individual services, Amelia does not allow a separate add-on to be included as an option. I am looking for a solution that does this because I don’t want the add-on to be part of the package, but I want to make it an available option to purchase when someone buys a package of services.

I think you are requesting the same as the “extra” feature that only works on a service and not a package. I wrote: “A service can have an extra added to it but not a package. Any work around?
Example:
A customer can purchase a 1 x 60min service and have an extra popup asking if “Do you want add extra +30mins for $5 more?”
It would be cool if my customers could buy one of my MANY packs such as 5 x 60min services with extra option “Do you want to add extra +30mins to each session for $25?”
“
This would be good
I agree and also for events can we add on a tshirt for example