The carpet padding is available in different thicknesses. I've seen it as thin as 1/4".

The link I posted on the noise foam will sell it in smaller quantities than listed also. It still probably wouldn't be practical for only one or two machines. I bought enough to do a couple dozen to cut down on shipping cost.

Still not the same?  

Could you send me a link to the material you're talking about? I'd like to see if there's something exactly the same on my side of the pond. However, I agree that the other material might be a good alternative, and I don't mind buying a lot of it as I've got many machines that I would apply it too.

Many thanks. Now I know exactly what to look for. I have found a similar material here, but not as thick as 3 mm. No matter, I'll start by looking at the local store's laminate flooring section and see what they have. I had previously looked in the roofing department because they have felt-like materials there too, but none of it seemed like the right thing to be gluing inside a typewriter case. Even the felt that I linked to in a previous post would work well too I think; it certainly looks very similar to what was originally installed in my machines.

Some typewriter manufacturers used a thin cork (about 2 to 3mm) as sound-deadening on portables (Oliver springs to mind), so yes, I don't see any reason why that wouldn't work !

My Lettera 22 had a disgusting smell when it arrived. I sprayed the felt parts with kitchen anti-bacterial Dettox spray, and when that was dry, (by hairdryer) used antibacterial foot odour control spray on the felt too. It really toned down the stink to the point where I could actually sit and type! I have avoided ripping out the original felt stuff for fear I would never be able to find anything near as good. The underlay sounds great, and I'll try it out on my Silver Reed which is extremely noisy.