All my bikes have straight posts. Take the clamp apart, rub beeswax on everysurface, tighten hard, real hard, it won’t move. Maybe check once a year. Not a problem.
Does anyone know what an Ideale number 3 saddle clamp is? Those will solve the loosening problem completely, though you should do the beeswax anyway.
The only good steel post was the early Campy. For a Strawberry it should be a Titan or Reynolds aluminum post, polished. Of course if you polish a basic Kalloy straight post it looks about the same as the old ones.