Suggestion 1: With such a huge opening (90x75mm), may be some of those 8x8 LED matrix in 4Ledx3Led arrangement? So 22.5mm x 25mm slot for each of those LED matrix. The top can display current, the bottom can display voltage, and with 4 high, you can also get a DS3231 and display the date/time + temperature.
Suggestion 2: Better yet, get one of those LCD display and you can have a digital meter display as an analog meter like those dials in the airplane cockpit - and/or digital at the user's command.