Thanks for helping me out!  In the meantime, I discovered:

Anyone can get their radio code for free direct from Mitsubishi by telephone.  You will need the following information:

Last 8 characters of your VIN #
Radio Serial Number

Call Mitsubishi:

1-888-mitsu20 (1-888-648-7820), option 1, option 4
Current hours:  6am to 5pm Pacific, M-F.

Tell representative that you replaced your battery and now need your radio code.  If you are not currently a registered owner, they will ask for your info for registration. 

How to find your Radio Serial Number

It is located on a label on the radio.  You will need to remove the dashboard panel covering the radio.  For my Mitsubish Eclipse, it was easy (might be same for other vehicles):

Remove the two screws located underneath the radio. Just go to the edges of the radio and follow it down going underneath the dash. You will need a small philips head as there isn't much clearance especially on the left side. You can then pull away the plastic exposing the radio itself.  The plastic panel just tugs straight out from the dash.  Pull out the bottom first.  Then tug the top straight out, to pull it away from the snaps holding it on.

The Mistubishi representative asked me for the Radio Serial Number only, not the Radio Manufacturer's Number (MR...).  The serial number was visible for me without removing the radio itself (unscrewing it from the dash).  However, you might want to leave the panel off until you get your radio code in case they ask you for the MR # and you have to unscrew the radio from the dash to see that part of the label.

How to enter your Radio Code
(Courtesy of mittech)

Use the first four radio station preset buttons to enter the code.

1: Push radio preset#1 until first digit of your code appears.
2: Push radio preset#2 until second digit of your code appears.
3: Push radio preset#3 until third digit of your code appears.
4: Push radio preset#4 until fourth digit of your code appears.
5: Push either tape or cd button.

What to do if your radio says OFF instead of CODE
(Courtesy of mittech)

If your radio says OFF it means you entered the wrong radio code three times. To get it to say CODE again do the following.

1:Turn the key to on or accessory.
2:Push the power button so that the radio display says OFF.
3:Let the car sit for 1 hour.
4:The radio display will go blank.
5:Turn the radio on and it will say CODE again.
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