I did this modification a while ago but I have not yet written a post on the steps I took in the modification.
You can acquire theses nifty cameras off ebay or at flea markets. The problem is they use batteries that are lets just say very expensive and hard to find. However wait there is a solution. Most models take a 3.0v or a 4.5v power sore depending on the model. The AAA battery is a 1.5v power source.
Steps originally taken from the following link go here for specifics on the mod.
The most important part of this camera is the back where the Polaroid process occurs. Unfortunately my camera had film sitting it for who knows how many years. The chemicals look to of rusted and caused the paint to flake so I tried cleaning it out whit painters tape the best I could.
Next step is to take out the old corroded battery… Hope it did not corrode the wires to bad.
Next you will need to remove the internal plate from the camera. Note Learned the usefulness of doing this after the trial and error of modifying my Polaroid 420. You will need to remove 3 screws and the latch plate.
Now with a cutting utensil cut out plastic so the 3 cell battery pack will fit.
Now we need to create a 4.5 v pack because we had to buy a 4 cell pack one cell needs to be cut off. The problem with this is the 4th cell completed the circuit so we need to do a little soldering to take the place of the lost cell.
Now solder the pack in and insulate the wires and we are good to go..