Ceramic/Mylar cap replacements

[Electronic M]

It's ok to put 2 half capacitance same voltage caps in parallel to make an unavailable value.

Personally I'd look for the same type of cap, but I would widen my search to 1% to 10% tolerance (a cap that is within a 5% tolerance is definitely within a 10% tolerance). I'd also be open to any voltage rating between 200V and 1000V.
Voltage rating of a capacitor is basically the maximum voltage you can continuously apply across the part without destroying it... A cap that's harder to ruin shouldn't be a problem... The only exception to that is electrolytic caps which usually want at least 50% of their rated voltage to last their rated life.