ATM Making a finder scope

["bill kocken" <wmkocken@hotmail.com>]

Hi all.
I'd like to build an 8x50 right angle correct image finder scope for use on
my dob.  I know I can buy one for $80 to $100 or so, but this is the ATM
forum after all!  I think I can buy a 50mm objective with a focal length of
200mm or so, or extract one from an old pair of binoculars.  I plan to use
an old 25mm eyepiece from my first scope. Is there a good way to put
crosshairs into the ep?  I expect I can assemble the pieces with PVC
plumbing stuff. I have access to a nice set of rings.
The question is, what kind of optical piece do I need to turn the optical
train 90 degrees and present a correct image?  Does anyone know of a good
source?  If you've got plans for one or a webpage, let me know.

As long as I'm doing this, should I make something bigger, like 60mm?

Thanks,
Bill Kocken