I'm posting this here so this mod can have it's own thread, hopefully making it more easy to locate for anyone interested...
I recently found a thread on this site referencing a cheap eBay-purchased flashlight that had threads compatible with the Sipik SK68. I ordered this flashlight, and was happy to find that it worked perfectly!
The flashlight was purchased via this auction: http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=220894394485&ssPageName=ADME:L:OC:US:1123
Since purchasing, I have found what appears to be the exact same flashlight at Manafont for $4.20, listed as the "Small Sun ZY-203". I have not purchased this light to confirm that the threads are the same, but visually, it is identical to the eBay purchased light, including the same generic LED, press-in 'pill', and tailcap switch/boot. If anyone purchases this light to test, post here so I can update this topic to include that info!
A bit about the light; it's a VERY cheap and poorly built C3 clone using a typical generic "Super Bright" 5mm-type LED. Threads, machining, fit, and finish are extremely low quality. I tested this light using 1xAA, 2xAA, and just for kicks a single 14500 cell. The light emitted the same (low) amount of light in all configurations. The light output is comparable with the Super Bright 7-1/7-2 lights which are much smaller and more handy for EDC use.
On to the VERY simple mod:
This mod uses the main body tube of the flashlight, not the included battery extension tube. While not a perfect fit, the tube still threads very securely into the Sipik allowing a second AA cell to be used. I threaded the end with the longer threads into the body which improves the fit. As an added benefit, the tailcap/switch from the sacrifical host is retained this way allowing you to replace a flaky/damaged/difficult-to-unthread switch/tailcap on your SK68. Just keep in mind that the light is compatible with a SINGLE 14500 cell; management will not be responsible for the return of any magic smoke released when you try to use two 14500s using this mod.
A possible minor added benefit is that in this configuration, the clip can be reversed allowing the light to be clipped to the brim of a cap. This light is much too heavy and extends too far forward to be ideal as a cap-light, but it DOES work if you absolutely need your hands free.
<edited to add> The tailcap of the eBay light I received was recessed enough to allow the SK68 to retain its tailstand-ability after the mod...
<edited to include>Per user Paranid below, this host from eBay is also compatible, and is considerably cheaper:http://www.ebay.com/itm/3W-White-LED-2-AA-Handy-Camping-Flashlight-Torch-/250638302599