All the Yetis come with a solar regulator built-in.
Any solar panel may be connected to the input, as long as they do not exceed 22 Volts (which most 'camping/caravan' panels don't). You will probably need an adaptor cable to suit the Yeti. You cannot connect panels that have built-in regulators, as the regulator needs to 'see' the battery to function, which it won't if connected to a Yeti.