"add ons to" is correct and usable in written English, usually as part of a larger phrase
For example, "We offer special add ons to our basic package to give customers extra features."
Experiment with different add-ons to find ones you like.
At the moment they are seen as add-ons to existing networks.
Nagy has been experimenting with online add-ons to his course for years.
They are best appreciated as add-ons to a meal, not a culmination of it.
Experts can help decide which windows and doors to arm and which add-ons to include.
It said add-ons to existing stores boosted the like-for-like figure by 0.9%.
Add-ons to the Maya ruins of Copán and Tikal are available.
We asked professional photographers what items were the most useful add-ons to a basic camera and lens.
The deal with TSMC would have let other companies attach their custom add-ons to Atom chips.
"Without those add-ons to the daily rate, it's difficult to make any money in the business".
He is also considering holding "Bookend" events, which happen over several days as add-ons to the festival, throughout the entire city, not just Brooklyn.
