You're fine...
175/70 = 185/60 = 195/50, at least pretty close. your tires have a taller sidewall, so are not as good at cornering, but given tire choice in 185/60 yours may not be all that bad. Better mileage anyway. So relax and drive the snot out of them.
OR, if you really want to change them out, 175/70R13 is very common on many older VWs and other european cars, and you can sell them on to someone else if they're in very good shape.