The link JayGTD sent is complete but seems very expensive! I bought them through eBay as Booth11 has suggested, paid 15 for all of them. Installation is simple (link posted by Booth11), but fiddly, takes a bit of patience.
To adjust footwell intensity, mine didn't work at first but at the second go it was fine. Try doing it when you're parked and the ignition in ON position (i.e. engine not running). As you might have noticed intensity can only go up and down in 5% steps, bring it upto 50 or so at least to see a difference.