A small back pack pattern should work - the type I'm thinking of zips down each side, so it should open up big enough to set your serger in. And it would have straps for carrying it. Something like this:
http://www.byannie.com/purses-and-ba...-day-every-way
Another suggestion is this pattern for a carry on, but it might be too wide to stop your serger from sliding about, which can be avoided by using a tie down strap inside or padding the machine with fabric and supplies when transporting.
http://www.byannie.com/purses-and-ba...ate-travel-bag