If you are talking about the top motor mount on the top passenger side of the motor they are available at many auto parts stores for a whole lot less than a dealer will charge You can view a video on replacing it at YouTube under richpin06
right side of motor where the engine mount is
In the owners manual or shop manual. Get one from MOTORLIT.COM
I could not find price for removal and install, but the motor is $1699.99.
When you have a bad motor mount you may feel a thud when you try to change the gears of your car. You may also find that your motor moves a little because it isn't secured to the car properly.
You can find the 1991 Nissan starter motor relay switch in the fuse box. The starter motor relay switch will be in the third column, second from the bottom.
First thing you must do is find the motor mount that needs to be replaced as there will be three of them on there. Once you have found the problem motor mount you must loosen up the other mounts so that the motor will move a little. Now using a jack raise the motor up far enough to get the broke mount out and replace it with the new one. retighten the remaining bolts and finish up.
Look on the radiator side of the engine, behind the motor mount.
You can find your vehicle specific motor mount at your local auto parts store like advance auto or Auto Zone. Or just visit your local autoshop and have them do the work for you.
Try Haynes Repair Manual for the Saturn S-Series 1991 thru 2002 available at most auto parts stores.
E-Bay?Hemming's Motor?
Trouble is to get it mounted right. It'd be very rare to find an assembly spot set up to accept both flange mount and foot mount. But assuming the motor spec is the same (power, RPM, etc) it'll work just find assuming you get the alignment right.
You can find wiring schematics at your local library as they usually have motor manuals there.