I believe Swix has a bag that handles 4 skis.
Be careful if you are planning to pack all the skis in one bag for air travel, and keep the bag well under max allowed weight limits so as to not raise flags -- technically the airlines only allow one pair of skis/poles in a bag, and they can get picky if you have more than one pair in the bag.
Many of us travel with two pairs in a bag, but every once and a while someone will get busted and have to pay extra. If the bag is well under weight limits, you have a better chance of staying under the radar. There may be size limits as well, but I am not familiar with all the various airline rules.
Snowboard bags work well for multiple pairs of skis if they're not too long. The Burton Wheelie Gig bag is good, and comes in various lengths up to 181cm. My wife has the 166cm bag, and it holds her skis and a bunch of other crap with room to spare. I saw that bag on www.brociety.com/ for $40 last week, which is a steal. There have also been some Swix ski bags on www.tramdock.com/ recently.