As the title says I recently broke the plastic cover that goes over the speedometer. I looked online and I could only find replacement for the whole cluster. Do they sell just a replacement plastic piece?
I should note that the KM versions of the speedo are made of cheaper plastic but they do work. And they are all for 2001+ versions of the bike. The electrical harnesses changed after 2000 so they aren't plug and play for pre-2001 TWs.
When I first picked up my TW, I discovered that some small ants had decided the speedometer housing to be a great place to build a nest. I used an Exact-O knife to slowly cut through the glued seam of the housing in order to access the odometer and clean out the ants and larvae. I think if you do the same thing, you can take it one step further and remove the clear cover using the same method. Then, take Errtu's advice and custom fit a new one! You can do it, and welcome to the forum, brother!
My dad and i replaced the glass lens on his klr250 speedometer. In his case, it was a huge pain in the ass because the glass was held in place by a seperate plastic flange that gets fused to the speedometer housing after the glass is set in place. We had to cut out that plastic piece and grind the inside of the housing flat so we could put a new shaped piece inside and rtv it in place.