You don't have to find another island, you can go back to Athens and then rent a car to visit other places inland.
But if you are not interested, there are several possibilities from Naxos with daily ferries.
Only from a logistical point of view of travel without talking about details (beaches, visits, hikes, atmosphere, authenticity) specific to each island.
- Tinos: 2 hours from Naxos
From Tinos it is possible to return to Athens either by the port of Piraeus or by the port of Rafina
(about 4 hours by ferry)
The particularity of returning via the port of Rafina is that you are a few minutes from the airport.
Leaving Tinos for Rafina the day before your return flight to Canada, you can sleep one last night at the Avra hotel in Rafina which offers a free shuttle to the airport for the next day.
https://tinosecret.gr/en/
- Sifnos: 2 hours from Naxos with ferries that make this connection usually at the end of the day (on their way back to Piraeus).
https://www.abettergreece.com/sifnos/
https://www.roomsinsifnos.com/
From Sifnos you are 2h30 from Piraeus by highspeed ferry and about 4h30 by traditional ferry.
New ferry connections are planned for 2023 on this Western Cyclades route, these are not yet announced.
- Amorgos: About 2h30 from Naxos.
It's the furthest island from Athens among the three. The Amorgos-Athenes trip lasts from 7h1/2 to 9h depending on the ferries.
https://amorgos.gr/
Hope this gets your travel planning mojo back!
