You will need this adapter for the Nova Vista Liberty/Seneca Aspen/Air Venturi Avenger/ Umarex Origin. Make sure to use a suppressor one caliber size up. Works really well and reduces the chance of pellet clipping.
https://donnyfl.com/products/nova-vista-liberty-1-2-x-20-a50?_pos=1&_sid=f2bf63f03&_ss=r


 I recommend the Sumo .cal? 1/2x20.

https://donnyfl.com/collections/ldc/products/1-5-x-6-5-inch-sumo


If you do not want to remove the suppressor for filling, I recommend the KOI .cal/ 1/2x20.

https://donnyfl.com/collections/ldc/products/1-22-x-7-inches-koi