Basic UI design

I have a piece of software I wrote but I am awful at user interface design. The layout is set, essentially I just need a designer to generate a mock up of a possible [login to view URL] current colours are the general colours I am after but you can add any greys, slates, blacks or whites. I literally only need colours, maybe modifications to fonts and slight adjusting to margins etc. Should take a decent designer no more than 30 minutes to come up with something. I require an image file which I'll then use to replicate the design in Windows Performance Forms. The software drops down from the top of the screen when a user moves their mouse to the top. Usability is our primary goal.