Those Draeger tubes look like a viable solution, though it is a bit pricey for home use. The pump looks to be $600 for the cheapest version then $70 per test for the tubes.
The reason I am asking is I am wondering, with the application of selective catalysts to vehicles throughout Europe and the US, if there is a cheap way for the home mechanic to determine the efficiency of the urea injectors. $650 for a troubleshooting tool is too much for that purpose.