Elecom only works with Wii Les Paul, and not always either.
The only adapters that work are Raphnet (out of stock currently), Emio (no whammy or joystick support on that one though) or Arduino-based one if you know how to solder.
The Pi Pico is generally cheapest at $4 but that depends on your country
Edit: I thought I was replying to someone else. This is the cheapest I know that works, but it will not let you use whammy or tilt https://www.amazon.com/gp/aw/d/B073HPD5TC?psc=1&ref=ppx_pop_mob_b_asin_title
Tilt/Whammy doesn’t work but you can map both of those features. Excellent alternative while waiting for a raph. Grab a USB Extension as well.
You'll want a USB extension as well but here https://www.amazon.com/gp/aw/d/B073HPD5TC?psc=1&ref=ppx_pop_mob_b_asin_title
https://www.amazon.com/EMiO-Edge-Gamepad-SNES-Mini-nintendo/dp/B073HPD5TC
Whammy/Tilt star power does not work. It works fine other than that. You'll need a Male to Female usb cable as the adapter is very short.
EMiO Edge Gamepad for SNES Mini - Super NES https://www.amazon.com/dp/B073HPD5TC/ref=cm_sw_r_cp_apa_i_KNAsDbNR9G9FK
If you decide to go wired. My wife has hers working with the adapter from this and an USB extension.
For most guitars, some kind of adapter. For Wii, there are a few options, the best being the Raphnet but they're usually out of stock lately. This one works (yes you buy the whole thing just for the adapter), but without tilt/whammy, and the cable is very short. There are other adapters that may work but I haven't tried.
Option 3 is a standard Wiimote with Bluetooth, either built in to your PC or with an adapter.
Option 4 is my favorite but takes the most work and soldering: mod it with a microcontroller