This sort of question comes up quite regularly.
The Pentax trigger voltage is quite low, and I would not want to take a chance; particularly when there are a lot of genuine Pentax flashguns around. When I asked the same sort of question a year or two back, I was told that any Pentax flash is safe on any Pentax DSLR.
If I want more power than the built-in flash, I have an AF240Z that slips straight on and works. Alternatively, I use an old Vivitar flash that connects through the PC socket (but I don't know if the K-x has one).
The Pentax AF240Z seems not to be a particularly sought-after flash, so for a cheap unit, it could be worth looking out for one.
For a definitive answer, search the forum for posts by mattmatic.

Geoff

Interesting to see city of Industry described as a "small town" (Vic Cross, above). When I bought my first computer motherboard (from a Chinese family running their business out of a double lockup garage in Industry) the city was in fact six (some people said seven) non-contiguous areas located roughly north of the 60 Freeway, and east of the 605 Freeway. It was incorporated in order to prevent adjacent Cities from attaching the unincorporated parcels of land for tax purposes.

Joshua - California is a big state, so do tell us which part you come from, please.

Vic - I seem to have a vague recollection of someone with the same name as yours, from my days on two wheels (but they were 50 years ago). Any comments?

Geoff

I bought both the cable release and the wireless one from 7-Day.
Chrissinkpen and I spent a little time testing the two of them and they both gave the autofocus function before release.
Chris went on to use the cable release during a Studio Night at our local camera club - no problems at all.
Geoff

Make one.
You can get the 2.5 mm stereo plugs and sockets from Maplin, and if you don't have a soldering iron they will sell you one as well.
Three-core cable is technically better, but you can use four-core and just ignore the fourth core.
i was just about to make one myself, and the Guernsey 7-Day Shop came up with a wireless one similar to the one that Algernon suggested (and for a lot less than £20). I believe that they are currently offering this again.
Geoff

Apart from the Motor Drive A, it will also take the Winder ME II - which is easier to find.
I think it handles like the originals (think S1a, for example), but will work with K, and KA lenses (and, of course, M42+adapter).
No, I am not parting with mine.
Geoff

And the charger arrived exactly as described and very well packed.
Thanks Pawel.

Geoff

PM sent.

Just one thought:
Remove the screw and spring, fit the adapter with a trace of Loctite, fit lens to body and screw in firmly. Leave for a while. now you have a permanently adapted lens.
BUT
If you don't have an auto/manual switch on that lens, you will have to find a way of locking the iris pin down or you will be stuck at full aperture. I used a small piece of cable insulation to adapt a 135mm Hoya - so that I can turn it back to a normal M42 auto lens again.

Geoff

Follow davidstorm's advice and use a flush-fitting M42 to K adapter
>run it on with a tiny trace of Loctite on the thread
>install lens onto body and then tighten it well
>leave for an hour or two, and then remove gently.

But first:
Does the Chinon have an Auto/Manual switch?
If not, and you want to use the iris settings, you will have to go into the mount and lock the iris mechanism down.
I used a short piece of insulation from some electrical cable (slit lengthways) to slip round the pin on the inside when I converted a 135mm Hoya to K-mount.

The mount screw-holes may be the same, but I think that the iris mechanism may be different. It is easier to focus and then stop down to what you want.
Geoff

For a Pro with (say) several hundred images to download after a wedding shoot - yes, totally agree.
For an amateur with maybe 20-30 images - half of which will be dumped anyway - then speed is not the only criteria. The speed with which a computer can render the image can outweigh that of the card-reader, for example. Perhaps, the speed of the card itself is more important (some high capacity, but cheap, SDHC cards are only class four, for example). Shooting DNG + jpg I can look at the jpg quickly and decide if I want the DNG image, and if not, delete both of them. That way, there is no real time penalty involved in downloading unwanted images to the computer.
Geoff