I read here and in another website that the Tent of Meeting likely would not have used the skin of an unclean animal, since touching such an animal [Any and all parts of it??] or preparing such to make a covering would make the person unclean. Apparently, John the Baptist wasn't concerned about covering himself with the skin of an unclean animal, wherever he had gotten it; but then he also wasn't trying to enter the Tabernacle thus clothed, before Jesus' sacrifice and resurrection that would declare 'all foods clean' (Don't know about skin coverings). That's what made me wonder if in fact an unclean animal's skin such as that of a porpoise (deflecting the unclean elements outside?) would or would not have been an issue for God in the days of the Old Covenant.
The Bible is very clear on what an "unclean" animal was which you will find specificially in Leviticus 11. It is indeed specific to being EATEN not used for clothing. A great example of clothing being fur and being used is found in Genesis after Adam and Eve sinned. It is not specific on which animal was used. The IMPORTANT thing for the Jews was to know which animals were unclean to eat. I honestly believe a lot of this was due to health concerns of those days.