Hi one of the best boxes to use with mxkey is UFS box. You can get the box with or without hwk.
If you just want to use it with mxkey just get UFS3 box with out hwk. They sell them on ipmart for 25 USD, check below.
UFS3 TORNADO BY SARAS : Buy UFS3 Tornado by Saras (Without HWK and Cables) - from IPmart.com
Kind Regards