I am now getting to the point in the design where I need to hammer down exactly which configuration I am going to use for the spectrometer..  I've been sorting through tons of documents trying to determine the best configuration balance for cost, complexity, and resolution, etc..  

I am fairly convinced at this stage that the Crossed Czerny-Turner configuration is the best fit for this application with all things considered.. 

Finding optics on eBay is slightly hit or miss...  Locating the mirrors haven't been easy, and I think I may have to resort to purchasing new ones...Fortunately, they're relatively cheap.  Here's what I am presently considering.. 

25mm Dia. x 50mm FL Protected Aluminum, Concave Mirror $37.50 each

I may revisit this since I have to work out the focal lengths, etc..This means that I will have to revise my diffraction grating, and some optics...but that was to be expected anyway..  This document was a great deal of help in making this decision Imaging Spectrometer Fundamentals for Researchers in the Biosciences––A Tutorial ..  As was this http://www.ibsenphotonics.com/technology/spectrometer-design-guide and the comments in my bio, thanks to everyone who offered information.. it is appreciated! 

As for a detector...  I have done some more research.... It seems the Sony ILX511 and the Toshiba TCD1304AP are both popular..  Ocean Optics uses them..  And you can get them both on eBay for $15.. I've been throwing the idea back and forth about designing my own driver, etc or integrating the dev board from the company and interfacing to that, or at least the middle ground of that and using their design on a custom board..  Time will tell there, when I get that far..  Ultimately, I'll be shooting for a configuration that results in an output like this mercury-argon calibration spectra...