linuxcnc 4-20mA driver solutions

I have a 4-20mA device (250ohm), and I was wondering if there are any hardware solutions available to drive 4-20mA devices?

I am fairly ofay with 4-20ma control, and can fabricate something, I was just wondering if anyone knew of a linuxcnc hardware solution (like a Mesa board or something)

thanks in advance

The simplistic answer might be analogue 0-10V out through a 5k resistor (with an offset applied in HAL to give 4mA for 0 input). That isn't a very good current loop, but if the device is driven by a PID that might compensate.
Otherwise I guess that an off the shelf current-loop driver IC is the way to go. For simplicity this would probably be driven by one of the LinuxCNC analogue output devices, though SPI or similar feel like they should be possible.