Check at
www.juststrings.com. You may need to email them. I know they have a 4 strings set of Chromes for 32 inch scale basses that would work, but I do not know if they have a C in that scale you could nuy extra. You might could use a regular 34 inch scale one, providing that you could stick a little more of the string in the body at the bridge end before sticking the pin back in.
Another route....email Michael Kelly and see what they would suggest.