Hi,
Why do you want one? For pocket carry only?
Own any sharpening stones? Sandpaper and popsicle sticks?
I don't own that particular one, but they're all mostly the same,
overpriced/limited / easily outclassed by a $1 cheapest stone
... unless you're looking for something very compact
and shaped exactly like this Sharp-N-Spark
More of my thoughts and those of others in
Pull through sharpeners?
and
Knife sharpening with slot devices
Consider this video,
a guy selling a non-slot version of a tungsten carbide sharpener,
sharpening old/superdull knife,
says in the video even hes not pigheaded enough to spend hours with his product
so he bought a dollar stone and used that instead
How to use a Whetstone the fast way - Sharpens Best
So, these things work, but they're not stones

Depending on where you shop $19 buys a lot of sharpening stuff and fire stuff

for example
Most of it fits on your keychain,
cut out the ceramic v-slot sharpener from the cutting board
tape the ligher to the flashlight/opener,
... only $4 plus ~$.40 tax