Amplified Handset Solution for GXP-2000 and hearing impaired users.

I have one user who is hearing impaired and would like to have an amplified handset for his phone. At the moment we are using GXP-2000 phones, and i would like to keep the environment homogenous. Is there a handset amplifier (not headset) that is compatible with the GXP-2000? Ideally, i would like a solution that looks "integrated" and clean as this phone is used by the president of the company.

(side note: As a test, i used a traditional amplified handset, and there is not enough voltage to power the amplifier.. Pretty much what i expected...)

Thanks in advance!