Hosting Home Domain- PLEASE HELP!

Hey everyone, i’ve been searching all over the internet and haven’t been able to find anything about this, hopefully someone will be able to help: I’m going to be hosting a webpage from my home computer. I will also register the “IP:port” with some service (prob no-ip or somthing similar). It will be up most of the time, but during the times that I turn the computer off and the website goes offline, I want a domain that would detect that and redirect to a custom 404 page or a completely different domain. Obviously this 404 page couldn’t be hosted on my PC because it would be disconnected all together.

So in other words, I was wondering if anyone knew of some kind of domain or redirection service that would provide this option. Any help on this topic would be greatly appreciated!