I went with the ebay tablet approach, and got a low firmware switch to boot! Plus, it was actually in *better* condition than my main switch! Wait for a 15% off ebay coupon (every week or two, works on almost everything in the store).
The downside to this is that I wanted to hack originally to dump all my carts and avoid having to swap carts all the time. Obv I can't do that on my second switch unless I update that to a newer fw *and* make it my main switch and find a way to xfer my saves (so have to hack my main switch)... all of that defeats the point of having a second switch, so I'll just keep cartridge swapping I guess.
Before anyone says to buy digital - carts are cheaper (BB GCU 20% off and $10 preorder bonuses), come with their own memory card so don't waste space on yours, and can be easily swapped among me and my 3 kids, who are all switch obsessed. I foresee more switches in my future for all these buttheads. I probably won't ever resell my carts, but I could if I wanted to, which lowers the effective price even further. Those advantages outweigh (for me) not having to swap carts, so I put up with the small inconvenience. I only complain because it is easy to ignore a game when it isn't right there in front of you, in favor of one that is, so some games can end up languishing just because I don't want to go downstairs and grab the case.