[red-beard]

https://www.apc.com/shop/us/en/products/APC-Universal-Transfer-Switch-6-Circuit-120V/P-UTS6

Seems kind of expensive for a maximum of 20A.

This seems interesting

https://amazon.com/dp/B07J5JXFGH/ref=sspa_dk_detail_4?pd_rd_i=B07JVBZB2Q&pd_rd_w=3SAqh&pf_rd_p=45a72588-80f7-4414-9851-786f6c16d42b&pd_rd_wg=CS9tG&pf_rd_r=6766SGQJXFJFG5NX4XK9&pd_rd_r=728c5b7a-3059-4c70-a728-7f5492face90&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzQlFNOFVIR1lNM1U3J mVuY3J5cHRlZElkPUEwNjk2NjI0MzdMTllCT1VQWk5BTyZlbmN yeXB0ZWRBZElkPUEwNzI1MjAwVUsyRzZURzFXT1U3JndpZGdld E5hbWU9c3BfZGV0YWlsJmFjdGlvbj1jbGlja1JlZGlyZWN0JmR vTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

Here is a very good small universal 30A 120V ATC

https://amazon.com/WFCO-Electronics-T-30-Automatic-Transfer/dp/B00B2AUZZC/ref=pd_cp_263_4/135-5984253-8195718?_encoding=UTF8&pd_rd_i=B00B2AUZZC&pd_rd_r=1e16b7d0-d60d-4801-9060-26c8db562a7a&pd_rd_w=OtfUt&pd_rd_wg=31UpO&pf_rd_p=0e5324e1-c848-4872-bbd5-5be6baedf80e&pf_rd_r=9QFA8YAYA01GGM83G21N&psc=1&refRID=9QFA8YAYA01GGM83G21N