The fan comes with the Reprapdiscount Hexagon it’s a complete kit. The fan shroud it came with was 3d printed in black, but I split it. I just printed another one in purple.
For the parts you need search the forums for Fangtooth and you’ll see some threads with links to the STLs.
Ya Steve thanks, I’m all over the threads so I think I know the one your talking about, well he linked me to the little blower fan, which I think is different than what you’rr using…
I have a Hex end on the way, completely pre-built so I shouldn’t have to source parts for that, but I also ordered an aluhotend from 3dindustries, not quite full on all metal hot end but it does required a dedicated fan. I’m sure any fan will do though,The specs on those little blower fans are only .58 cfm.
About the cartridge issue, just using a bit of deduction and brainfarting here, the block “absorbs” and “transfers” (the physics terms, eck, been too long) the heat of the heater cartridge right? And the amount of that absorbtion and would depend on the density and chemical make of the material, ie Aluminum, the “transfer” of that energy would be affected by this also but I think would be effected by size also…
A good way to think about it would be to take it to the extremes, if you had a thin piece of metal(aluminum) surrounding the heater cartridge, it would burn up because that materials size is too small(Given it’s density) to absorb, transfer and dissipate the amount of heat energy from the cartridge. Now if you had that same cartridge in a 12x12" aluminum block, the heater cartridge will still output the same amount of energy into that aluminum block, but because of it’s size, the absorption and transfer will be much different, more spread out, longer to absorb and longer to dissipate, but still technically will contain the same amount of energy being input into it…it’s just that the absorption and transfer phases have changed, and this is what we’re interested in, because it’s the transfer of energy from that aluminum block, that vibrates the molecules of plastic, that we want to have control over…
But that’s comparing a small piece of aluminum to a large 12x12" block, so in the scale that we’re talking about, comparing a 5/8" block vs. a slightly larger, 3/4" alum block, the difference is probably negligible…???
I see the only difference being, a larger heater block taking longer to heat up, because a larger, longer heater block means more material to heat up, YET, it would be in contact with more of the cartridge body, so the change would almost cancel itself out.
Although, If you wanted faster heat up times, I bet you could just have a small “cylinder” extrusion feature jutting out of the heater block, just to the full length of the heater cartridge, but not add all the extra material of the full block. This way you’re contacting the full length of the cartridge but are keeping the same size of heater block. 
I’m going to patent that 
Moral of the story, don’t accidentally touch you hot end with your hand or eyeball while you’re trying to fix stuff. 
SInce you seem interested, our hot end testing notes early in the Mini development phases can be found here: http://devel.lulzbot.com/mini/Azalea/Hotend_testing/
is there nothing left a secret with you people! 
that’s awesome though.