You can buy it from any retail store such best buy Costco.
To replace the ink pad please follow the below instructions.
Spread plastic or newspapers over a table and place your unplugged printer on it.
Remove the viewing panel. This is a panel on the back of your printer on the right side, held in place by one or two screws. On some printers, it will be a rectangular panel, and on others the whole right side of the printer will come off. Locate the screws, and using a Phillips head screwdriver, remove them. With a flat head screwdriver, carefully pry the panel off.
Find the ink waste tubes. These should be easy to locate because they will be two clear tubes running side by side into the ink waste reservoir. Some printers will only have one tube. One end of the tubes will be attached inside the printer and the other ends will be loose. Pull the loose ends of the tubes through the panel opening so they are hanging out. You may need to use needle nose pliers to accomplish this if you cannot easily grasp the tubes with your fingers.
Remove the old pad. This is a messy task, so make sure that the area surrounding the printer is covered with material that you don't mind getting ink on. You may wish to wear rubber gloves. Using the pliers, pull the pad out of the printer and set it aside. Clean out the reservoir by pushing paper towels into it and letting them soak up the ink.
Replace the pad. You can purchase a clean pad at a computer parts store, but they can be hard to find and expensive. You can also cut a new dish sponge to the proper size and insert it as a replacement. You may also try cleaning the old pad by letting it soak in a large bowl of hot water then squeezing it out. Make sure it is completely dry before putting it back in the printer. Place the loose ends of the tubes back into the reservoir the way they were. Most people, however, choose to make an external ink waste reservoir. To do this you will need to extend the tubes. This can be done by purchasing air line connectors and some plastic tubing to fit. These items can be purchased inexpensively wherever aquarium supplies are sold. If your printer has two tubes, cut two one foot long pieces of tubing. If it only has one tube, just cut one piece of tube. Insert the connectors into the ends of the tubes attached to the printer then connect them to the tubes you just cut. Then punch a hole in the cap of a bottle and insert the ends of the tubes down into it. A small, plastic water bottle will work fine. Now the waste ink will flow into the bottle and you can empty it any time you need to. You may want to attach the bottle to the side of the printer using Velcro or tape so it does not tip over.
Reset the counter and get rid of the error message. To do this you will need to download software. You can download it for free at ssclg.com. The link is in the resources. Run the program on the computer connected to the printer. It will allow you to reset the counter to zero and dismiss the error message. It is a good idea to read the instructions in the help file of the program before doing anything. However, once the program is downloaded, it will appear on your desktop tray and you can right-click it to bring up a menu of options. The second option is "Reset counters." Click on this to reset your counter and thus cancel the error message.