The Rock Band 3 MIDI Pro-Adapter will be released in the UK "late next week" for around £34.99 / €39.99, Mad Catz has told Eurogamer.
Mad Catz, Harmonix's official partner when it comes to Rock Band 3 accessories, said the MIDI Pro-Adapter will be available to buy from "all leading online retailers".
The PlayStation 3 and Wii version of the adapter will be released first, then the Xbox 360 version "shortly after".
The MIDI Pro-Adapter allows Rock Band 3 owners to use the Squier by Fender Stratocaster Guitar and Controller, due out in the US in March for $279.99 (around £175 / €199). The Squier is a fully functional, full-sized electric guitar with strings that doubles as a game controller for Rock Band 3's Pro mode.
The adapter also allows gamers to use "most real" MIDI keyboards and MIDI drum sets when playing the game. It plugs directly into the console via USB, converting the MIDI messages into console controller data which the game translates into on-screen action.
There's a velocity sensitive adjustment for MIDI drums, designed to reduce cross-talk during play, a full D-Pad and standard gaming controller buttons and a removable clip, which allows gamers to attach to a belt or rest on a table top or similar flat surface.
Meanwhile, Mad Catz said it was aware some Rock Band 3 owners were having trouble buying peripherals for the stunning music game. It promised 100 per cent availability from its own online store, Gameshark.
"Incidentally, we know that some folks are still finding difficulty getting hold of some instruments and accessories," a Mad Catz spokesperson told Eurogamer this evening.
"Mad Catz would like to remind gamers that we are the official partners with Harmonix and thus our webstore carries pretty much everything in the Rock Band range from software through to legacy instruments and of course the new Rock Band 3 products."