I am looking for a pushbutton matrix with at least 25 (more would be better) buttons.
Just ask Google for "Novation Launchpad". Something like that would be great, but I want 1. Just the buttons (with LEDs would be great but not necessary) and 2. Access to the raw data which can be processed by arduino or another uC.
If you know anything like that please let me know.
You can get 4 x 4 keypad matrixes quite cheaply, and 5 x 4 ones for a little more. Perhaps 2 of those next to each other? Alternatively, how about using a touch screen instead?
Scroll down to calculator keypad, 5x4 for $1.
I have not seen 25 button versions anyplace.
Not rocket science to wire up 25 tactile switches/push buttons in a 5x5 matrix tho.
Decide what footprint you want to use.
Switches are as little as 10 cents each.