triton T100si replacement?

hi can anyone tell me what triton electric shower i can replace my old triton T100si using the exact same pipe work, im not capable of changing anything myself so need to be the most easiest way possible . cant afford a plumber ( unfortunatly). I was told the rapide 4+ would be ok but im not sure. already brought one shower but was not the same line up for the pipe work, so need to be sure this time .