I'm in Zurich so maybe this doesn't help directly, but I had the impression Dos Equis was realatively common, at least in Mexican restaurants. I've been served it many times without even asking for it. I always considered it pretty common, at least by the standards of Mexican beers in Switzerland
. If you want it for at home, beer shops such as Beers of the World also have it.
If all else fails, check these people out http://www.amstein.ch
. I understand they're somewhere in the Lausanne area. It may be worth talking to them directly as they tend to have more stuff than they list on their website and can order stuff they don't have.