Update 2018-05-19: it died after almost 10 years of use and I have just ordered a replacement, looks like the same model: http://www.dx.com/p/precision-digital-pocket-scale-300g-max-0-01g-resolution-15004#.WwAq-3UjFhE
I first looked at ProScale but many of their affordable scales has an auto-off after just 30 secs. Then I found this post [home-barista.com] about this scale [dealextreme.com]. A sub $11 digital scale (incl. shipping from HK) with these specs:
Operation Modes: g/oz/ozt/dwt/ct Backlight: Blue backlight (with auto-off) Capacity: 1000 gram Accuracy: 0.1 gram LCD display: 5 bit LCD display Power: 2 X AAA batteries (sold separately) Length: 11.1 cm Height:1.8 cm Width:7.5 cm Weight: 101.4 gram