Thanks for taking the time to look at this and respond.
The diode I have in mind is:
http://www.diodes.com/datasheets/ds12009.pdf
It appears to be somewhere in the nano-Amp range for voltages below 20V if I'm reading that right. My application will normally run at about 10mA-35mA with occasional bursts to 135mA when writing to an SD memory card.
Thanks.