I find most any clown will host in a suitable anemone. The safest thing to do is to mate your clown with a species of anemone that is a natural host (and vice versa). Here's a good online source for that information: http://www.nhm.ku.edu/inverts/ebooks/ch2.html
Magnificas are available and sold as Rittari anemones, but they get HUGE (several feet across) and require A LOT of light and water current since they naturally occur fully exposed to plenty of sunlight and wave surges. They aren't ideal for captivity unless you have a tank dedicated to it.
Yup, Len is right, Magnifica is a difficult anenome to keep.Not recomended for a beginner aquarist. Here are some other species that are difficult to keep S. Gigantea......... S. Mertensii
Here is a link that has some great info on anenome care and clowns that will host in what types.
Hmmm cant get the pdf file to upload. Can we upload pdf's here Len???