differential routing without GND
I need to route 100ohm differential pair [...] for parallel routing on one layer. I can't find any PCB calculator.

That is because a one- or two-layer board without prepregs leads to ridiculous track width. 70mil and wider with 10mil spacing. (I had once seen an USB hub with such a stackup. It worked for a while, then it began destroying random devices, obviously because of other design errors.)

You need a ground plane right below the impedance-controlled pair. Rule of thumb: 0.35mm prepreg, 8mil track width, 8mil spacing → 100Ω impedance.