I work with the Educational Collaborators network. They develop custom differentiated learning webinars all the time. You might want to contact them regarding this. EC has several folks who do these workshops. We typically like to know more about what you are looking for before figuring out who would be best. If interested, drop Karen Montgomery a message at firstname.lastname@example.org.
Sorry for the commercial. EC is comprised of educators, like yourself. It's really good stuff.