Are they any good?
Yes, the genuine Hakko 47X model basically is the base design that has been cloned like crazy out there, just like popular soldering station Hakko 936.
Are parts (and consumables) easy to get?
In my country, yes, there is an authorized Hakko distributor that is still selling parts for discontinued models, just watch closely at the last photo of the printed manufactured date of Hakko part labels at ->
HERE , its clear Hakko still manucfacture parts for old discontinued product.
Are they reliable (why are they missing the guns).
With my limited experience since I've been using it just few months, I found out they're very reliable, as long you clean it regularly or diligently
.
I did tear down mine as I received it 1st, and fixed it too, imo its very-very well made based on my observation of it's internal parts & design.
Apart from the suction main compressor, which I believe is the most expensive part, the 2nd most is the heating element at the guns, as its integrated with the stainless steel pipe for the suction, and probably thats why the guns is missing as they're quite highly priced even used.
Also genuine Hakko gun are very well made and built, as this needs a high precision mechanical parts that make it reliable to do suction work, and also don't leak around like cheap clone, as I've used clones before.
Are there other guns on the market that can be (relatively) easily adapted to fit and has anyone done this?
Suggesting to download the Hakko manual, observe, learn and look for the connecting parts like the vacuum hose and connector, and the heating element compatibility like the resistance and etc before ordering.
The 474 that I bought few months ago, and made thread ->
HERE.