Hey James,
The original run of Maestros (the 3 volt and 3 transistor FZ-1) was from 62-65 where Gibson made roughly about 5000 of them. They didn't sell as Gibson had anticipated until Keef recorded 'satisfaction' with one after which they became highly sought after by guitarists and studios of the time so they then released the updated FZ-1A which runs on a 1.5V power supply and has different transistors (3 x 2N2613 or 2N2614). They made roughly in the region of 35,000 of these. The FZ-1 is therefore harder to find but recognisable by it's lower serial number and 2 x pencil battery holder. Prices for the occasional ones that come up on ebay would be in the region of $650-$1000. FZ-1A boxes (which very many of the garage punk/psyche kids would have used from '65-'68 ish) come up reasonably frequently on ebay and would usually cost around $350-$600 depending on condition. Problem is that so many of these originals have been butchered to 'improve' them as short sustain became a problem for the newer generation of blues rock wailers. As long as they have their original transistors that still function they can be restored to their original glory but if the trannies have been replaced you're in trouble! Originals are a gamble for sure, and even perfectly functioning ones can sound quite different as consistency was not easily acheivable in those days. The early noughties reissues were apparently pretty good but they actually sell for in the region of $170-$250!
A modern day, accurate (original NOS transistors) clone of an FZ-1A that will be both reliable and sound pretty much bang on would be the Creepyfingers 'fuzznugget' which I believe would be in the region of $250, and Jerms builds a frighteningly accurate FZ-1 clone for about $350 or thereabouts (if he agrees to make one!) Of the various clones I have using non-spec transistors I would recommend the Ghost Effects FZ-1 clone which costs approx £120 - it captures the 'feel' of a maestro really well. But for the cheapest cheerfullest yet pretty decent FZ-1A clone then the North Effects Primitive. Only £75 which is honestly as cheap as you'll ever get to come reasonably close to an original.
As far as other fuzzes go to try to acheive the Maestro sound, I suppose something that has a voltage starve, bias or gating type of control will help get in the ballpark of that short sustain grindy buzz, which could be helped along if you can drastically cut bass frequencies. You'd be struggling with a fuzz factory as it often gets too synthy sounding on the gated settings, and most other fuzzes based around other classic circuits (perhaps with the exception of the MkI tonebender...) just aren't really going to get you into the right territory. The MI audio 'neofuzz' has a bias knob that helps get close to the right sort of feel and I'm sure that with a bit of tweaking you may be able to get a rough approximation with many other modern designs (Basic Audio does some pretty cool sounding buzzy fuzzes at a very reasonable price, unfortunately I don't have any of his boxes).
Costs a lot of money to sound this cheap!