If your sis wants the cellphone to be like the gophone, what she can do is buy the gophone, ask some techie guy to work on the gophone so that it can function as a normal cellphone and at the same time she can become a Go-onger as well, presumably Go-onYellow ^^my sis wants to have a cellphone like the gophone
another question: what cellphone models will likely to fit in it?
^ What he said.
Plus it would be likely be pretty expensive.
Your sister will likely be better off getting/making a Go-Onger theme for her phone (i.e. wallpaper, ringtone, backgrounds, etc).