If you want to replace the switches, the trick will be the neutral. If you have a neutral in the box you can use almost any smart switch, but you will probably have to add a pigtail to the neutral bundle to make the connection to the switch. Without a neutral your options are limited.
If you want to check out the Zooz switches I have an advanced driver post with links to all the product pages: [DRIVER] Zooz ZEN Switches Advanced (and Dimmers)
One of their switches should work OK on a bath fan, would have to look at the specs. Also the ZEN30, the bottom relay button can work on a fan since its a dry contact.
