The K1 4-band (KFL1-4) board was discontinued

Unfortunately Elecraft company no longer offers KFL1-4 board.
It was from June 2014. Of course I wanted to buy it in August to upgrade my two bands K1...
The 30m band would be good for SOTA activation when 40m band is occupied by a contest.

First information I found in Elecraft e-mail reflecor.
mailman.qth.net/pipermail/elecraft/2014-July/205670.html
mailman.qth.net/pipermail/elecraft/2014-July/205685.html

radiopreppers.com/index.php/topic,824.0.html

The main information:
"The 4-band board was discontinued due to a part availability issue that
>was  crucial to the functionality of the KF1-4. So no, it will not be coming back  sorry to say < (Lisa from Elecraft)"

There is also an official information by Wayne N6KR
"The 4-band module requires extremely low-temperature-coefficient trimmer capacitors because of its narrow-band pre-mix and RF band-pass filters. The last source for these exotic trimmers dried up recently. A redesign using higher-TC trimmers might be possible, but the filters would end up being triple-tuned, which would force the use of SMD components throughout, and tuning the filters would then be very difficult without a spectrum analyzer.
 
Sales volume for the K1 has decreased in recent years due to the KX1 (which is smaller and has a DDS VFO), and the KX3 (which covers all bands, all modes, with up to 12 W output and has a much more capable auto tuner, nicer user interface, etc.). So the cost of a redesign wouldn't be recovered.
 
That said, for the time being we're continuing to offer the two-band version and the other options (KAT1 ATU, KBT1 battery pack, etc.). The K1 is one of our "full" kits, and has a bit of a fan club of its own.
 
We'll update the website to reflect the change in option availability."

:(