The K2 Travel Kit used to include an LDG (link) Z11 QRP Autotuner. The Z11 is a latching-relay version of LDG's original QRP autotuner and draws no current once a match has been made. Here is a description of the Z11 from its manual:

The Z11 is a full featured low power automatic or semiautomatic antenna tuner designed for the HF ham bands (1.8 to 30 MHz). It will work with virtually any transceiver or transmitter providing between 0.1 and 30 watts continuous RF output (60 watts SSB or CW). The tuner uses the highly versatile "Switched L" configuration with 256 capacitor, 256 inductor and High/Low impedance settings to provide over one hundred and thirty thousand possible tuning combinations. The "L" network will match practically any coax-fed antenna (dipole, vertical, sloper, beam, etc). Long wires, and dipoles fed with ladder line can be matched using the LDG RBA-1 external balun, sold separately. Regardless of antenna type, tuning time is between 0.1 and 3.0 seconds, typically about 1.5 seconds.

The Z11 uses latching relays to switch tuning components in the "L" network. These relays hold the tuning configuration even when power is removed; once matched, the tuner automatically enters a low-power mode where it draws only 0.8 milliamps. Placing the tuner into "Standby" reduces power consumption to zero; the latching relays maintain the tuned configuration indefinitely. During tuning, the Z11 may draw up to 300 milliamps, but only for a few seconds. These exclusive LDG features make the Z11 ideal for portable, battery-powered HF operation.

The Z11 uses a 2.5mm x 5.5mm coaxial power plug. I had made a parallel power cable to enable me to conveniently power both the Z11 and the K2 from one source.

UPDATE: I had discovered that the Z11 wasn't working accurately; when it thought it had achieved a better than 1.5:1 match, I measured up to 2.2:1 SWR with an external SWR bridge. I performed a calibration according to the procedure sent to me by the LDG technician but this didn't significantly improve performance. I sent the Z11 back to LDG for diagnosis and repair, fully expecting to have to pay for this service. I was shocked and pleased when the Z11 came back to me repaired and upgraded to firmware version 1.6 (memory tuning upgrade), at no charge. That's customer service!

(Here is the Z11 manual as a 1.6 megabyte PDF file as downloaded from the LDG web site and here is a link to the firmware rev1.6 memory tuning upgrade being offered by LDG.)