The smallest "music" recorder is the Yamaha Pocketrak 2G:
34 x 120 x 13 mm, 49 g including one AAA battery
But I wouldn't recommend it because it doesn't sound very good.
In addition, it's so small that adult fingers have some difficulty
using the controls.
Its larger brother, the Yamaha Pocketrak CX, is a better choice:
47 x 130 x 18 mm, 92 g including microSD card and one AA battery
This is about the same weight as a HiMD machine, and its long
and narrow shape fits easily into a pocket.
This Pocketrak CX also doesn't sound as good as the R-09 or R-09HR,
but it's the smallest recorder with OK performance. At $400, it's an
expensive little bugger.
There's more about the CX here
http://taperssection.com/index.php/topic,105902.0.htmlThe Yamaha web page is here
http://www.yamahasynth.com/products/pocketrakcx/index.htmlFlintstone