I'm not sure where H2X got his domes, but basically what SwissMicros uses are plain standard metal snap domes, which can be ordered on a lot of places and replaced quite easily (at least compared to other defective switches). Luckily the SwissMicros calculators are "built for disassembling and fixing with a screwdriver", which is quite rare today, but really worth the money.
For the ones which are interested in the topic:
This guy fixes a single snap dome in a old phone. This could be also interesting too for people with old HP calculators, I guess. Anyhow I wouldn't cut-out the old metal dome with a carpet cutter. But maybe that's just me. I'm also parking my car in a shady place on a sunny day. So...:
This guy explains the layers of membrane switch with metal domes. Quite interesting for those who would like to know something about the basics of these sort of switches:
However, I personally got the second DM42 which has less switch problems, but still has. According to the S/N, there are 164 units between the first and second one. I must guess this is a serious problem over a lot of units (or I have the fortune of negative "lucky punch").
I really hope Michael can provide all of us which are affected with replacement foils as he wrote on 14th Feb. That would be really the easiest way to fix it.