The suggestion by Kozlok bears a lot of merit. I forgot to about that. The K-01, K30, K50 and K3 have the focus peaking capability. Coupled with your macro lens, it will show you on the rear screen just exactly what is in focus. The K-01 would be the easiest and cheapest in the $200 range. With 16MP you could print natively up to 20" by 30" easily. Using the Perfect Resize utility, you could enlarge to what ever size poster you could ever need.
Also, one advanced aspect of product photography would be a tilt/shift lens. These are very expensive - there is a Samyang 24mm Tilt/Shift in a K mount that goes for $1000 that just came out. You will probably not need it, but its an option.
You can also get a small HDMI monitor to attach to the camera, so that you will have a much larger screen on which to frame and focus your shot. They come in all sizes from 5" on up, portable or desk top - here in the US, office stores sell 20" HDMI monitors for $100.