I spun up my own version of this REF200 Current Reference Circuit in KiCad. It was inspired by
http://www.scullcom.uk/category/projects/low-current-reference/ It has four ranges - 100uA/200uA/300uA/400uA.
I was able to use just two jumpers to create all of the permutations and combinations of the switch. See the notes on the schematic. This created a "real estate" savings and avoided the (considerable) cost of the switch. The PCB is just 12x19mm, IIRC, and can be had at OSH Park for $1.85/3 Copies/Shipped-(Anywhere, I think.)
My version is intended to be strapped to a 9 volt battery, with a rubber band. The Lead/Probe pads are large enough to forego the banana jacks.
I highly recommend SamTec brand high-temperature header pins, for the jumpers and such.
I could use some help with proofing it, for the 434 time... <g>
Anyway, you are free to do anything that you wish with the attached KiCad Project, given my release of liability, of course. See below.
WARNING: RISK OF ELECTRICAL SHOCK AND AUTHOR IS NOT AN ELECTRICAL ENGINEER.
FREE FOR ANY AND ALL USE, PRIVATE AND COMMERCIAL, GIVEN THAT THE USER WHOLLY INDEMNIFIES, RELEASES AND HOLDS HARMLESS ALL AUTHORS AND DISTRIBUTORS FOR ANY AND ALL CLAIMS, SUITS, JUDGMENTS, AND THE LIKE, INCLUDING COSTS OF DEFENSE, ARISING FROM, OR OCCURRING IN CONNECTION WITH SUCH USE OF ANY AND ALL PROJECT MATERIALS. SHOULD USER PREVAIL AGAINST ANY AUTHOR, OR DISTRIBUTOR, CONTRARY TO THE INTENT OF THE ABOVE, USER AGREES TO ACCEPT LIQUIDATED DAMAGES IN THE AMOUNT OF $10 AS FULL SETTLEMENT THEREOF.
EDIT: TYPO CORRECTED;
MIDIGATED = LIQUIDATED