Add Modal to end of Navigation Bar

Site URL: https://www.fpvisuals.com

I have a modal button that opens as a popup.  I want to add this button to the end of my navigation bar but only on certain pages. 
Im not sure how to go about doing this.  

Hi. You can add this to end of nav, then we will give some code to show it on certain pages.

If you don't know how to add on end of nav, you can use this plugin to add lightbox on navigation item.