Better get the troll response of Kid Icarus out of the way (for reference they had to ship it with a stand, and even then many a veteran games player still complained of hand pain).
Anyway 3ds has no games as far as I am concerned. If you hacked your 3ds such that you have DS and GBA then I can do more.
That said I would ask what constitutes tiring for you as different mobility losses and whatnot play out differently for different people in my experience. Is it more holding tense/ready for action or just long term?
Turn based stuff is usually a good start, however if you have one that sees you move a few hundred pieces per turn (not so many but some) then that might be harder.
You need not be restricted to that and plenty of real time things work for a lot of people here, if you find one you can put down for a while to recover then even more becomes available.
Similarly visual novel type deal might be a start, but holding one of those for hours on the sofa (particularly in 90 degrees rotation) can be fun. A book stand could change that.
Also is the sort of thing that could be helped by having a giant shell around it? I have met those that have a hard time holding an awkward DS designed to be a pocket device but controller weighing the same is fine. Not sure what is out there in the way of clip on shells these days, or whether you could abuse on of those mobile phone clip on devices for this but I note it anyway.
It is also where emulators come in as well; playing on PC brings all sorts of things as far as controllers (foot controllers are a thing),
cheats, scripts, savestates, slowdown, turbo and more.