The N64 probably never saw any traction in China. Really, only the PS2, newer handhelds (DS, PSP and beyond), and current generation of consoles have had any real presence over here, despite still being technically illegal. You’d have more luck going to Hong Kong or looking on Taobao. Outside of some party heads’ kids, I doubt anyone has had one in China that didn’t bring it over from somewhere else.
You ain’t gonna find it at a second-hand shop, is what I’m sayin’
You might find one of those iQue things which is basically a controller with an N64 emulator and a bunch of preloaded N64 games, but I don’t think that’ll serve the purpose you want.
Here’s a bunch of N64’s on taobao, I couldn’t find smash bros for it though. A lot of Melee and Brawl, though!