I think that they have **Seifert fiber space** presentation as:
$(On,1|(1,b))$.

Or
$(On,1|(1,b),(a_1,b_1),...,(a_r,b_r))$, if you allow an orbifold with cone points in $RP^2$.

You can look at the cases by decomposing $RP^2=Mo\cup_{\partial}D$, so the orientable 3-manifold will be the

1) orientable $Q=Mo\tilde{\times}S^1$, the

**twisted circle bundle over the mobius band**, very well known being equivalent to the

**orientable I-bundle over the Klein bottle**, with boundary a torus $T$,

2) and a

**Dehn-filling** in the remaining disk $D$, with a whichever fibered solid torus or tori.

We could say that $(On,1\mid (1,b))=Q\cup_T W(1,b)$, for a fibered $(1,b)$ solid torus $W$