As Piesync was sunsetted and Hubspot Operations Hub is the tool Hubspot has for integrations, that would be where you’re pointed to for this project.
Vertify, we’re a Hubspot partner, does this set up. We can work with you on which ever situation your in: do your customers live in multiple SFDC instances or are they separated and don’t ever need to cross over.
Happy to talk more if you like to see how we’d go about.