I've used Anki for Japanese too. My solution: rdp/vnc to my home server. Probably not an ideal solution, but easy if you have a home server. Besides, running Anki from the same source makes it possible to continue on a set i've already started but not finished. Perfect for 40 minute public transport rides to/from campus.
There's a port of Anki for the N800/N810 (http://ichi2.net/anki/wiki/Anki%20on%20Maemo). Why don't you ask them if they'd do a version for the N900. You can run it directly from the source (it must be Python), so you could also try downloading the source and running it--it might work.