I want to make a button in the navigation smaller

Hi there!

I wanna create a donate button for an NGO on my website in the upper right side of the menu, but I can't get the button to be less than the height of the navigation.

Ot actually I can, by decreasing the height of primary navigation and increasing margin of other menu items, but than my logo becomes very small and that's not cool either.

Can you help me with this?

Cheers,

Piet