It's pretty difficult to emulate an N64 with both accuracy and speed because its GPU is strange and flexible in all the wrong ways. And its game catalog isn't that large, so not worth the engineering effort.
The games people care about deeply like SM64 have remakes that aren't that hard to get.
I saw an SGI Indy on eBay today, that had some sort of N64 development device it came with. Not sure if it actually contained an emulator or maybe just a header for an onboard debugging port though. Sadly it was priced wayyy higher than the Indy I just bought so I ignored it.
