If you are handy with a soldering iron, you could build your own V/I converter using a chip like the XTR110 from Burr-Brown: http://kolter.de/xtr110.pdf

Because you need to source 4 mA of current with zero voltage input, you will NEVER get there with a purely passive network of resistors.

[This message has been edited by NJwirenut (edited 08-20-2006).]