I would think any MIDI controller with ample programmable knobs would also have the capability to do what you want. Any controller which has a pitch and mod wheel should be able to give you both manual control with the pitch wheel and automated control with the mod wheel (where the higher up you set it, the stronger the vibrato would be, which is what I think you want). However, you may have to program the envelope shape for that effect and/or assign it to the mod wheel, possibly from presets that come with the keyboard if it comes with them at all. As long as you're sending MIDI data to one of the channels available (1-4 since these are the default channels assigned to the four GB channels in mGB), it should register on that channel.
I personally haven't done this so I'm only speculating but I do compose in FL Studio to control GB and NES and I know for a fact that pitch is determined by the channel level pitch control (not a specific MIDI CC) so unless your controller uses something other than standard MIDI (unlikely if it was made in the 90's or later), I don't see why it wouldn't function that way with mGB as well.
As far as specific hardware, I would check out some YT video reviews of light MIDI controllers and see which ones have the features that would allow you to do this. Andrew Huang has reviewed a bunch and I recall seeing one that looked perfect for this use but can't seem to locate the video at the moment.
Unless of course you want something that is a stand alone pitch/mod wheel that can 'intercept' output MIDI from a separate device (be it another external controller or a computer running a DAW), in which case that sounds to me like a homebrew job as I haven't seen anything like that before that also lets you designate specific channels. Having said that, and I could be wrong, but I believe you can use some external controllers as a slave wherein you can apply parameters not being applied by the master MIDI source (that is, if you're playing a composition from a DAW that doesn't have pitch parameters set already, there will be no interference from the slave controller). And that controller, theoretically, can be anything that has a programmable mod wheel (or pre-programmed with vibrato envelope), channel specific designation and can be set as a slave MIDI device (not MIDI through).
Also, I rarely use MIDI hardware in this way so forgive me if none of this is accurate lol. I just saw no one had chimed in yet and thought I'd offer that I do know if it could help at all.
Last edited by Doctor Octoroc (Nov 21, 2019 6:21 am)