U can go down to a 165/50/15 if you want something real close to the original rolling diameter, but a decent brand 195/50/15 will work, thats what ive got on my ute, but it every so often touches the front bottom corner of the wheel arch of the guard. I run a stanza front disc set up atm.
You could also try a 185/55/15, im swapping to these, i just have to fit them. U could even go for a 175/55 i think.

Ultimately i would be fitting the 165/50/15's on the front(potenzas) and probably 185 potenzas on the back or maybe a 195/45 as they are grippy and you dont really need much more with a decent tyre, but they are up around the 200 mark a piece. But u will generally need to order them in so testing may not be an option. Most tyre shops wont carry the more uncommon sizes, but u can get them.