You might be able to use a Supertex LR645 high voltage linear requlator.
See the following web site:
http://www.supertex.com/products/selector_guides/107/100
I have been using Alberta Printed Circuits (www.apcircuits.com) for several years. The Canadian dollar currently has a depressed value which makes their prices very attractive. Their price includes overnight delivery and two day processing.
Most Silicon Photodiodes respond to wavelengths between 400 nm and 1000 nm. This can be a problem is you are trying to ignore visible light. Try www.photonicdetectors.com as a starting point.
