Easier to find the original C3 wooden stock and mod it. (edit: these look to be about 60-100$ on canadiangunnutz)
http://www.snipercentral.com/c3a1.htm
the scope might be tricky to find. (2nd edit: looks like the ZF69 will be in the 200-250$ range if you can find one, I didn't see a Unertl sale)
Stuff like the slings and stock spacers are easy to find.