8BitDo’s latest Retro Receiver brings wireless controller support to the Nintendo 64.

The new $24.99 adapter plugs into the N64’s front ports and serves as a wireless bridge for modern Bluetooth controllers ...
EDN

Developing a N64-Gamecube Controller to USB Adapter

A standard HID joystick is being implemented in this project by the microcontroller firmware since Nintendo 64 and Gamecube controllers are excellent controllers for several PC games. A standard HID ...

8BitDo Revives The N64 Controller With A Wireless Twist And It Works On The OG Console

BitDo refreshes the 8BitDo 64 controller released for Analogue 3D with a cheaper 2.4GHz version that pairs to an adapter—though the adapter is also sold individually for use with standard Bluetooth ...
Ars Technica

N64/PS2 -> USB adapter. How do I make it work?

I have this adapter. It is auto-detected just fine in XP. If I connect a N64 controller to it, it works fine. However, I can't make the PS2 controller work. When I switch the adapter to the PS2 side ...