Written Endorsement CGX?

Trying to figure out the endorsements to take my commercial written. I am an ASEL pilot and have taken my CAX written and scored a 98 on it but now am thinking I want to do my commercial glider as my initial commercial cert, I like the focus on stick and rudder skills and energy management. I used Gold Seal for my commercial prep and the endorsement is specifically for the Commercial Airplane written. Do I need to take a specific glider commercial course for the ground portion? I’m not opposed to ASA Prepware if that works.

And another note- is there a Sheppard Air equivalent for the CGX test bank? No sense in leaving anything to chance.