Where would one purchase a dugong skin?

Exodus 25:3-5 says this in relation to getting materials from the people of Israel to build the place where God shall dwell with man.

And this is the contribution that you shall receive from them: gold, silver, and bronze, blue and purple and scarlet yarns and fine twined linen, goats hair, tanned rams skins, goatskins, acacia wood...

The funny thing is that the Hebrew doesn't actually say goatskins. My ESV footnote indicates it is 

Uncertain; possibly dolphin skins, or dugong skins, compare 26:14.

Which raises the question "Where would you get a dugong skin?"

A theory via Gordon via Andrew Barry and Adrian Russell: The Israelites picked them up as they were travelling through the Red Sea.

Not sure if this is possible but the timing seems about right, and what a reminder whenever they looked upon the roof of the tent over the tabernacle of the way the God of Israel had delivered them from slavery.

Plausible? One for the mythbusters among us.