Doesn't get much simpler than this two terminal current source/sink \/
"A JFET can be made to act as a current source by tying its gate to its source. The current then flowing is the IDSS of the FET. These can be purchased with this connection already made and in this case the devices are called current regulator diodes or constant current diodes or current limiting diodes (CLD)."
If you can find a 22.00 mA and 22.50 mA source you could wire them to subtract.
Never built one of these \/ https://en.wikipedia.org/wiki/Widlar_current_source
but you might work through the equations to see if it will work for your application. I know some manufacturers make matched transistors in one package.