I'll be interested if you do find a good source. I use Malarone regularly, and it is fiendishly expensive....but it works. Haven't found any way around the expense, though sometimes I can persuade my insurance to kick in for a portion of the cost. FWIW, it's my understanding that Malarone is considered safe for long-term use, though this may not yet be reflected in the official dosing recommendations.
Doxy is cheap, but the side effect profile doesn't really work for me, and you say you can't take it anyway. Mefloquine has twice failed me (i.e., I contracted malaria), but like most people I never had any trouble with side effects, and it's ok to use for extended periods. Chloroquine and other old-line medications are more or less useless except within certain very specific areas--and even in those areas, the CDC/WHO tracking of resistant strains seems to lag on-the-ground experience by a few years.
The artemensin derivatives are not approved yet in the States, and they are very subject to counterfeiting and adulteration, at least in Africa where I spend a lot of time. There appear to be programs on the way which would bring artemensin prices down and drive availability up, but these are as yet unrealized. I don't know how this currently works in Europe.
And there's always the option of going unprotected but carrying a curative dose or two; this hasn't ever sounded very enticing to me, but if the alternative was to buy two years worth of Malarone (±US$7000/person) I'd probably reconsider.
Actually, I should mention that I have found significant savings in collecting unused Malarone from other travelers, either by donation or by paying less than the official price. Shelf life is long (longer, in fact, than indicated on the packaging). At the moment I'm stocking up for my next trip: I just bought a couple of packages from someone in Australia for about US$3/tablet, shipped to me in the States. On other occasions, friends and relatives have given me their leftovers. A surprising number of people are sitting on a couple of week's worth, wondering what to do with it but unwilling to just throw them away.
Are you really expecting to spend 2 solid years in malarial zones? One of the advantages of Malarone is that I can stop taking it whenever, for example, I go up into non-malarial highlands for a few weeks. This can add up on a long trip.