MMANA does what you want and it's free.

However, note that because MMANA being a MiniNec based program, when
using none vertical elements below 0.2 wavelengths accuracy rapidly
drops. If you'd like to optimize on (lower) HF, a Nec based program is
prefered

Furthermore, I don't think optimization is out. But, if it should be
so, it still will learn you very much about the effect of antenna
dimension changing on antenna performance.

And last but not least, because of being freeware, experimenting with
MMANA or 4nec2
[http://home.ict.nl/~arivoors/] will cost you nothing (besides a
little studying), weather you would like to use a traditional optimizer
of a genetic algorithm based optimizer.

Arie.