I don't think $1/x$ is what you want, since it goes asymptotically to zero, not to one (and it is negative when $x$ is negative, not positive like you want). How about a scaled version of the arctangent on the right side (which constant would you use to scale it?), $-1/x$ on the left, and linear function in between?
Another possibility for the function on the right is $x/(x+1)$.