I don't know specifically what they used - there are tons of RV Sofa's available online. The tough part is getting one the same color as the sofa you're replacing.
I do know that other members were eager to purchase the EasyRest sofa once it was removed.
Search for: Flexsteel RV sofa 60 x 75 (at lease that's the size of my EasyRest sofa)
When we first got our Adventurer we went down this road. But after living with the EzR sofa for 6-months. We like it and have gotten used to the small space when the slides are all in for driving.
Check out this one:
https://www.etrailer.com/RV-Furnitur...00024-025.html