Create Once-Off Mobile Version of Website

I created a 'brochure' website with Dreamweaver CS6 and PVII addons many years ago.
It looks fine on a desktop and laptop and is not too bad on a tablet.
It is however, it is very difficult to view on a mobile phone.

As a once-off project, I want to create a simplified mobile-only version
of the website (leaving the original www.site.ie as is.)
This mobile version would, I presume, be .... m.site.ie

I know a responsive/adaptive redesign of the entire site is the proper way to do the job,
but I am not prepared to do that near the end of my career for a single website.
(Besides .... the available budget is quite limited)

Do I need to insert a piece of  code in www.site.ie to redirect to m.site.ie?
Where is my m.site.ie stored on my hosting provider?
Any suggested tools & tips?

I use www.blacknight.com for my hosting.