https://www.dickssportinggoods.com/p...E&gclsrc=aw.ds
This is what I used for my 14' Mistral, and have carried it over to my sunfish for "towing" on the Broads. Small to stay out of the way (on the sunfish I bungie it to the mast) but can expand to get the leverage I need.
My rule is always get back to shore before 6pm on a good sailing day or you will be stranded because the wind will die and then you have to paddle.