You have a bad idea here, anyt of the suggestions will be a losy solution you will quickly abandon.
Any OB strong enough to drive a Soling will be too heavy to horse around when you need it. A 4HP would work fine, but borrow one and trid carrying it to the stern of a Soling and handing it over the end to someone, while staying on the boat.
If you feel you must have an outboard, sell the Soling and buy a boat designed to carry an OB, a Soling is not one.
Or keep the Soling and get two paddles, and go sailing.
Certified...in several regards...