Mugen seems to be gone. Last one i searched for and found was located in south africa.
On the other hand for the size of mugen i like to have a even bigger battery. If i remember correctly it was bulky and much unused space..
Azkay made a very nice mod http://talk.maemo.org/showpost.php?p...3&postcount=38 but didnt use 1400ma of space and he had a mugen cover.

And for the former price you might even consider a back cover with more functionality http://talk.maemo.org/showthread.php?t=95814 (i heared you like it bulky)

Currently im using the cheap solution.. just a spare battery.
But charging, changing, carrying is annoying!!!

Using another battery is hard cause of the N900 small form factor nearly all other batteries out there dont fit.

Maybe we should hire someone to carve an n900 (neo900) worthy 10 years anniversary solution.