aspheric or meniscus?

If I have a CO2 laser beam with a diameter of 3.8mm and I want to focus
it after a 3x beam expander to reach the smallest spot size, could I go
with a standard positive meniscus ZnSe lens or is it worth to pay for
an aspheric one? What could be the difference on the spot size? I have
to say I don't know how much an aspheric could cost, I've only heard it
could come at 4x the price of a meniscus. Do you know any ZnSe aspheric
supplier?
Thanks, Marco

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