comma or 'and' before 'with' [conjunction]: in skirts, with trousers

a. They were proud to appear in skirts that reached only to the knees and with trousers like men's underneath.

b. They were proud to appear in skirts that reached only to the knees, with trousers like men's underneath.

Are these sentences both acceptable?
I like (b) but the 'and' in (a) sounds a bit strange to me.

I prefer the comma version. To me, it more clearly identifies "with trousers..." with "skirts", rather than with "knees".

In the first sentence, "in skirts and with trousers" definately shows that they are wearing two articles of clothing. "in skirts, with trousers" makes me think that the trousers are part of the skirts. Looking at the shorter form, the comma doesn't seem to be grammatically correct so it does say "in skirts with trousers".