I'm developing a site in Joomla and SOBI2, and I need to search on checkbox group field similar to this:

http://www.mei.ie/index.php?option=com_sobi2&sobi2Task=search&Itemid=55&=1&=1&sobi2Search=search&searchphrase=any&field_county=all&field_null1=all&field_null2=all&search=Search

I need a Sobi2 standard plugin for make this.

Important: I need a plugin, not a hack in my site. For this reason, I not will make access to my server for you.