PC: O scale 2 rail PC diesel

[pamc@xxxxxxxxxxxxx]

List,
I am looking at building a small O scale two rail shelf
switching layout and
wonder where I can find a good Penn Central 2 rail diesel.
Would prefer a GP-38-2 but 
will settle for something else. Need something to pull my
Atlas PC caboose.
I've been in HO for years but not sure whats available in O.
Did some quick Yahoo search
but must be more out there, Brass maybe?
Thanks in advance for any help.
Kelly