MCR-SL-1CLP-I-I-00-4KV (Phoenix Contact)
MCR loop-powered isolator for the electrical isolation of current signals without auxiliary power, input signal: 0(4) ... 20 mA, output signal: 0(4) ... 20 mA
4-20mA input and Output isolator circuits are avilable in the market. If you can buy it, it is easy to fix, configure and use.
Try any of several from Mescon: