I know its not a Tenere tank bag but how about this
http://www.off-the-road.de/xt660_gepaeck.html?&L=1
(the first tank bag in pictures, price i think was normally about �80-90 or so)
its designed for the XTR and i got one from another forum member (FM)secondhand and its great. Is big enough for the odd bits and bobs when not expanded but when expanded still shocks me a bit by the amount you can fit in. Straps to the bike quiet good as the XTR's tank is mostly covered in plastic.
The only downsides ive got at the moment are it doesnt come with a rain cover even though it seems to be quiet waterproof so far. Once the tankbag is zipped off it doesnt have 2 schoolbag type straps, but has a good heavy duty single handle or a 1 shoudler strap, and the last this is the plastic see through top can not take an A4 page with out some of the corners being turned up/cut. Bit nit picking but thats my opinions.
Overall its a good bag but i wouldnt pay the asking price for it new. (Im a cheapo as well by the way)