Re: European pickups for 90s RI Duo Sonic
There are European (and UK) Duncan dealers, but yes indeed, their prices seem about double what we pay here. An SSL-2 (just to grab a very common pickup) from Anderton's is the equivalent of over $120 US dollars. They are $59 retail price here.
Any Strat form factor pickup with no stagger works, FWIW. Check European E-Bay sites for used pickups, perhaps.
Also, replace your pots before your pickups, and see what happens; those early MIM electronics can be real garbage. If you still think they pickups sound dull and lifeless, try doubling, or even quadrupling, the resistance on the pots (i.e. go to 500 KOhm or 1 MOhm pots). Also, try pickup adjustments.
Back to the Strat thing. The difference you hear between Jaguars and Strats is due to: 1) the fact that when you are hearing Jaguar pickups, they are almost always in a Jaguar. This means: A) shorter scale length B) much higher value pots in the Jag (4x Strat resistance, as I suggested installing, above), and C) much different attack and sustain/decay characteristics between a Jag and a Strat. 2) Lack of pole stagger. This changes the string-to-string balance.
Jaguar pickups are just flat poled Strat pickups without ears, with a different shaped cover, put into a short scale guitar with very high resistance pots. The metal claw has been proven to have no tonal effect (though it can perhaps provide a little shielding). Bottom line, you're hearing the major differences between a Strat and a Jaguar, not the major differences between a Strat pickup and a Jag pickup.
In other words, with all other things being equal (i.e. in the same guitar), anything you think a Jaguar pickup will give you is not actually anything special that a flat-poled Strat pickup cannot. Point being, you don't need pickups that are specifically designed to be Mustang or Duo-Sonic pickups. This opens up your options considerably; there are innumerable Strat pickups made, but only a handful that are specifically for Mustangs/Musicmasters/Duo-Sonics. Your only real consideration is that you want one pickup to be RW/RP, and that you want flat poles on the Strat pickups, so your undrilled covers will lay straight. You also could (but don't really need to) install small shims to take up the space under the cover on either side of the magnets, so the flat Strat magnets don't create a bulge down the middles the pickup covers. Or...just install the Strat pickups with drilled Strat covers, in which case you can put in any Strat pickup you want.
Classic Strat, Mustang, Jaguar, Musicmaster, and Duo-Sonic pickups are all basically the same inside, just with different accoutrements. Mustang/Musicmaster/Duo-Sonic pickups in particular are pretty much identical (Mustang and Duo-Sonic pickups came with one regular pickup and one RW/RP pickup, while Musicmasters came with only one pickup, of course). The biggest difference is that the Strat pickups had staggered poles, while all the others are flat (until the '70s, when the Mustang/Musicmaster/Duo-Sonic pickups were made with an evenly arched "sunken stagger).
Personally, I say just buy a pair of SSL-2s, one regular and one RW/RP (i.e. "middle"). They will be a lot easier to find, new or used, than any Mustang/Musicmaster/Duo-Sonic-specific pickup...and the only difference will be that the Strat poles sit slightly higher.
