Terry,
Rebublic Locomotive Works is about the only source for early decals that I have been able to find. Caboose Hobbies stocks their stuff. They are the old Robert Sloan line of decals. They aren't the best quality but you can make them work.
Larry Larsen graphics is working on some early D&RG stuff for me in On3 that he said he will offer in his regular line once they are developed.
CDS also does some dry transfers for the early D&RG billboard reefers that are actually quite nice.
I model the D&RG in 1880 in On3 and have searched high and low for anything pertaining to this time period and there isn't a lot out there. That is one of the reasons I do this time period though, it forces me to scratchbuild.
Good luck,
Gordon