You have linked to a site that is describing a suborder of animals, the Sacoglossa. The seaslugforum lists Sacoglossa as an order of animals. Either way, the division contains many, many individual species, and each has a preferred food source -- some only feed on a particular species of algae.
To purchase a Sacoglossa seaslug that will consume C. taxifolia, you are going to need to know which species in particular you are looking for.
If you are referring to the animal pictured, Oxynoe olivacea, it has been found to eat C. taxifolia, but its preferred food is C. prolifera. Also, these slugs suck the contents out of the algae but leave an outer "husk" intact, and thus will not completely "rid" your aquarium of the algae in question. You can read more here: http://www.seaslugforum.net/showall.cfm?base=caultaxi