I found this font Dina TTF which is originally a *.fon file for Windows. This version is a TrueType with only three bitmap strikes: 11, 12 and 13. Works like a charm in Netbeans.
Yet I am missing exactly one glyph, a left pointing arrow: U+2190.
I added it in FontForge, but when I generate the TTF, move it to ~/.local/share/fonts/TTF and update my font cache via fc-cache -vf ~/.local/share/fonts/TTF the new letter does not show up.
FontForge draws a green border around the new glyph and the background is crossed out, opposed to e.g the letter A which is not crossed out or framed.
It is not working because none of the fonts in the package encode U+2190 in any of the (Unicode) cmap subtables.
Try this: select a cell that doesn't have the red 'X' through it, go to Edit -> Copy Width. Then select the cell for U+2190, Edit -> Paste Into. The red 'X' for U+2190 should go away. Then edit the bitmap for U+2190 and regenerate.