How about using a galvanized steel trash can with a lid. Same effect as the safe you listed for about 1/10th the cost. As for solar flares damaging your cell phone:

Despite rumors to the contrary, a Faraday cage is not necessary to protect against solar coronal mass ejections because the frequency content of such disturbances is at much lower frequencies—they don’t couple energy efficiently into small-scale electronics, except through conducted paths (e.g., wires coming into the system). A better precaution against solar events is to unplug electronics and use quality surge suppressors.

Source: http://www.thesurvivalistblog.net/build-your-own-faraday-cage-heres-how/