This site gives details of ebook readers weighing less than 200g:
http://skinflint.co.uk/eu/?cat=pdapceb&xf=1366_200.
But in all honesty i could not recommend any of them. If you could increase the weight to 290g you could buy a Nexus 7 (2013) and have a magnificent tablet, not only to read your ebooks with but to entertain yourself during your frequent trips.
Of course you could consider the new Galaxy Note 3, but the price of this device is in a completely different ball park.
Good Luck and have a very happy New Year