PWM -> 4-20ma conversion

I’m working on a project where I need to control an existing industrial device that requires a rather precise 4-20ma input. I thought of getting a module from China that converts the Imp PWM output to 4-20ma. They specify incoming pulse frequencies in different ranges, such as:

D1: 50Hz-99Hz
D2: 100Hz-0.9 KHz
D3: 1KHz-9KHz
D4: 10 KHz-19 KHz
D5: 20 KHz-50 KHz

What would be a good range to pick in regards to the easiest range to control using the Imp PWM?

I originally thought about making a simple PWM to analog (mA out) circuit out of some junkbox components, but I really want to find something commercial that has some stability, accuracy, and durability.

If someone knows of a module or breakout board that accomplishes this, please let me know.

It really depends on how fast you want to change this input for the industrial device. If it’s only a few times a second I’d go for D3.