Changing Burger Menu Navigation Links Into Buttons

Hey guys, on my site i'm trying to change the navigational links on mobile to look like the enquire button at the top of the burger menu via CSS.

Any help is greatly appreciated!

site is: https://harpsichord-harmonica-ga8f.squarespace.com/

password: 123

heres a picture to show what i mean.

I want the two black links to resemble how the enquire button looks.

The website you shared is listed as expired?

Can't give you anything better without seeing your website, but this might be a start.

Custom CSS:

.site-wrapper .header-menu .header-menu-nav a {
  font-size:2vw;
  padding:1.5rem 2rem;
  border:1px solid #000;
  color:#fff;
  background-color:teal;
  transition:ease-in-out 300ms;
  &:hover {
    background:#000;
}