I use custom contact form plugin, I’m pretty sure there’s somewhere in there where you can assign an id or class and that would allow you to style it as you wanted. After looking at it, you would probably use there “Advanced HTML” option at the bottom of general settings and add in any classes or id’s you want into that text.
Aside from that there’s always wufoo you can have up to three free forms if i remember correctly, fully customizable also.
