I think the "Ugli Tomato" is a marketing ploy much like the "grape" tomato,
which started with the cultivar "Santa". I only find reference to it at
specialty grocers, If you find one, try to find out where it was grown, and the
name of the packer, We may be able to backtrack from there and find the
cultivar name. Many of the fancy tomatoes are imported from countries where
growers are quite secretive so it may remain a mystery for awhile.