I'm not exactly sure what you mean but....
Why not use symbols instead of the numbers? I'm assuming the number mean your fingers and in multi-tapping why not do something like
Ü - 1
ø - 2
Ä - 3
à - 4
for example? Or have I totally missed the point?...As for special fonts, the only thing I can think of is looking through some web sites...asking people who make their own fonts if they'd be prepared to make a "Tapping" font....
There you go, completely off the ball!