There are alot of ways to get this file. The common sizes of displays are 5x7 and 8x8. There's alot of places online where you can get ASCII 5x7 fonts, but I am making a scrolly display with 8x8's and I wanted to use the whole height of the matrix so I created this tool to easily format and create patterns and fonts and get them into the right format for C programming.
The attached file was created in excel and it has a couple of macros which make things easy. You will fill in the display area with 1's and 0's and then click a button and it will store your pattern in some cells below and convert everything to a hexadecimal string for popping into your C compiler or header file.
The attached file includes 5x8 fonts for A-Z, a-z, 0-9, some punctuation, and some awesome 8x8 patterns and graphics.
Not that it matters, but I am using the AVR ATtiny2313 and AVRStudio 4.16 with WinAVR GCC for controlling my scrolling display. I don't have it done yet but atleast making the font file was easy with this tool.
Check out the steps in this instructable to find out how to use the Matrix Font Generator