I found makerbot to be very helpful in the past (in the Bre Prentis days) with replacement parts... so it's worth contacting them.
It looks like the left side piece is a mirror image of the right side, without the motor and limit switch. Actually, the link you have on amazon looks to be the left side, not the right side, since the orientation is correct and there is no gap for the stepper motor, etc. (Maybe it is supposed to be Right, from the printer's perspective?)
Nevertheless, I agree this would be a good thing to model and print spares!
<*> Harlan