Hi ! The k-x is a great camera ( I own a stormtrooper one!) and I quite like it. as for a macro lens for product shot, I agree with you that autofocus will not be a must. I don't think your products will start moving around the table any time soon right?
I don't know how small and how close you want to take picture of your product. However, if your product aren't incredibly small, or if you don't want to take extreme close ups (to show a small imperfection for example) you can consider a macro lens with a magnification of 0.5 x (1:2). A true macro lens will go to 1:1, of course.
That being said, the Takumar 50mm f/4 would be a viable option. I am not an expert, but judging from what I read on this page of the lens database :
S-M-C/Super Macro-Takumar 50mm F4 Lens Reviews - Pentax Lens Review Database
there were 3 versions : the older one marked MACRO-Takumar, then, SUPER-MACRO Takumar and finally, the SMC-MACRO Takumar.
Only the first one, the MACRO-Takumar goes to 1:1 magnification. Again, only you know if you need that. 1:1 is very close, so it depends on what you will be shooting. Edit : The other to are 1:2 (0.5x magnification), which is suitable for most situation IMHO.
Then, you would need to use it with an adapter... the real one, from pentax, costs about 40$(I think...?) and if you are not in the US, can be a pain in the neck to get. Take that into consideration.
If you have a little bigger budget, I may suggest the excellent Tamron 90mm Macro. It is auto focus, newer, longer (not necessarily better for your needs though) and cost not that much more that a manual macro lens. You can get it for below 400$ BRAND NEW ! You can probably find a nice one used for less off course.
I hope it helps... but I have a feeling that my message brings more confusion into the matter that there was before!