Setting up a monthly plan with ad on options

I was curious if anyone out there has had any luck finding a way to create add ons in wix plan pricing, or if anyone knows a good third party app.

Example. I am starting a lawn care business. My customer wants basic lawn care every week, but she also wants to add our poo patrol service for an additional amount per month.

From what I can tell this isnt possible with wix, but I could be wrong. Any suggestions would be huge!