Sounds like you have a preference for "buzzy" (high frequency) vibes. When you read reviews, try looking specifically for the phrase "Buzzy". You may also like vibes that are slender or have a similar texture to the back of your toothbrush's head.
Another possibility is that the movement is what's getting you off, not the vibration. In that case, maybe look into the Eroscillator
. I don't think there are any other movement-based toys on this site, and it is quite expensive, though.
If all else fails, there's no real shame in sticking to the toothbrush. Perhaps look into rechargeable batteries or even a rechargeable toothbrush, although it won't really help you with the noise issue.