Searching for SunOS 4.1.3

[Chad D. Tillman]

An acquaintance referred me to this group because he thought someone here
could help me out.
 
I am looking for a copy of SunOS 4.1.3, preferably version C.

Can anyone assist me in finding a copy for purchase?  I have an old Sparc
with a program titled SNAP that was written for this particular version of
SunOS, but I do not have this version...only Solaris 2.0 and SNAP will not
run on it.
 
Thanks for your help!
 
Chad Tillman
chad at ti-law.com
704-458-2423