@fBoyle-- Just don't get a fan trellis. It will collapse from the weight of the tomatoes as they grow. I'm speaking from experience.
You can make your own with some conduit steel bars and string or twine that will go across both ends. This makes a strong, sturdy trellis for the tomato vines to attach to.
And remember that you need to weave the tomato vines into trellis as they grow. Although the vines will sometimes make their own way through it, you will need to lend a helping hand during the growing phase.