Add space between two pages on primary menu

I have a client that wants to have space between two pages on the primary menu, the Contact page and the Leasing Opportunities page. The primary menu is centered on the header, and he would like the Leasing Opportunities page to be located to the right side of the header/basically right aligned with space between it and the last page before it on the menu, the contact page, so that the Leasing Opportunities page is basically separated from the rest of the menu, yet still considered part of the primary menu… if that makes sense.

I found this CSS code:

ul#top-menu li.menu-item:not(:last-child) {
padding-right: 50px !important;
}
#et_top_search {
margin-left: 50px !important;
}

However, I am unsure as to what I would replace the “not(:last-child)” part of the code with so that the custom padding set only applied to the space between the contact and leasing page.
The theme I am using is Divi. I know how to plugin any custom CSS code through the theme setting, just am struggling to find the appropriate code for what specifically needs to be done. Help? Thanks!