You might be able to get acceptable output signal with any 5v Arduino, with an RC filter on a PWM pin.
You could use an external digital potentiometer controlled by an arduino of your choice. Or an external DAC chip, controlled by an Arduino of your choice.
There are some Arduino boards with a built-in DAC, but I think these are only 0~3.3v, so you'd need an rail to rail opamp to get 0~5v from that.
There has also been considerable discussion about doing the 4~20mA current signal here - I don't remember how to do that (I was never much interested - didn't have an application).