Yes, the Vespera range is compatible with all Vespera accessories:
Filters: Solar, Light Pollution, Dual-Band
Backpack
Tripods: High Carbon Tripod, Adjustable tripod
The Hygrometer sensor (sold as an accessory) is only compatible with Vespera / Vespera II and Vespera Passengers. It uses a different attachment system on Vespera Pro.
Vespera Pro, Vespera III and Vespera Pro 2 have a built-in sensor.
You can see the complete list of accessories here.