One part that you can pretty much never find is a replacement platen. The rubber on a lot of these old machines dries out and hardens over time, and can develop cracks such as the one in the photo. This typewriter was made by Remington in 1895, and is one of my current projects.
I won't delve into the details of all the work that has gone into this project -- instead I will focus on how I renewed this old cracked platen.
Step 1: Remove and Measure the Platen
The next step involved carefully measuring the diameter of the platen. I picked a spot where the rubber was still intact and used a caliper to measure the diameter.
Step 2: Get the Old Rubber Off of the Core
In recovering a platen you pretty much have two choices. You can try to find an industrial platen rebuilding service and, if they're willing to tackle your job it will cost you roughly $150 -- assuming they have recovering material in the size you need. This is too pricy for me.
The 2nd choice is to recover it yourself with a piece of smooth rubber hose. I have had success with this before on small diameter platens, but no one makes a smooth rubber hose in the size I needed.
So......I decided I needed a 3rd choice.
Step 3: Jumping in With Both Feet -- the 3rd Choice
I bought a length of 2" diameter heat-shrink tubing and began the process of building up layers.
Step 4: Building Up the Layers
Once it was fitting tightly (2nd photo), I trimmed the ends with a shop knife. I continued putting layers of the material on the platen and shrinking and trimming them until I had built up to the diameter I needed (this one took 5 layers). The finished product is in the 3rd photo.