Changing "register" button/links

[Edge83]

Hi all
I've had some luck so far using the admin searches for "register.php" but I have not been able to find yet where to change the link for the button or tab at the top right that says "register"

I am using digital access pass and the only people who can use my forum must be paid members. I have set it via usergroups so that "registered members" cannot see anything, but
I'd like any of the standard places VB links to register.php to link to the signup page on my site. I can't figure out where to do this with the "register" button up on the top. I have figured out how to do it when it appears as texts such as admin_required_register.

Thanks for any advice!