I use trays such as this two sphere one from glacio (when I got it it was around $30) to make clear ice.
Yes it takes a large amount of freezer space due to the need for the directional freezing but it does the job. I use filtered water, and store the cubes/spheres in a freezer bag. Note that these types of trays are not meant to be left in the freezer, as noted by @ScottinPollock you take them out after about 24 hours or else it becomes too difficult to separate the clear ice from the bottom frozen water.
