grep for it? The calculators in hh_tms1k have 7seg displays.
Looking at mirage_via_write_porta, the code here would something like:
u8 segdata = bitswap<8>(1 << (data & 7)),dp,g,f,e,d,c,b,a);
m_display->matrix(data >> 3 & 3, segdata);
and in the machine config:
PWM_DISPLAY(config, m_display).set_size(2, 8);
They will be output to "digit0" and "digit1"