I bought a BLB13 from Ebay last year around Nov, as i cannot find any in the usual shop like MS. CP... .
The price which i paid about S$46. an original in Ebay If i don't rem wrongly is about S$60-80.
I am not sure if it is real or fake. so far i use on my GH1, so far so good. take about 2-300 shots. It is as good as my stock battery.
I skip those Under $20 just to be sure.
Hope this help to you guys
Regards
Arthur