How to hook up two devices down with PoE? [closed]

My home network is currently setup in such a way that my cable modem is 25 feet away from my main router. My main router is about 35 feet away from my switch. I am planning to setup a central backup battery supply near my switch, so I started looking into using power over ethernet. I figured how to power my main router using a power injector for the ethernet cable from the switch end and a 12V 2A PoE splitter on my main router end.

The trouble is how to do I use a power injector for the ethernet cable from my main router to my cable modem. I would think that I need a 48V PoE splitter and then split the power connection to two. One connection will go to a step down voltage regulator (48V to 12V) to power my router. The other connection will be used to inject power into the ethernet cable from my main router to the cable modem. On the cable modem end, I will need a 12V 1A PoE splitter to power the cable modem. While this solution works in my head, I can't seem to figure why I can't find 48V PoE splitter on the market. Is there an alternative solution to this problem that I am not aware of?

Is this the type of thing you're looking for?

https://www.tyconsystems.com/poe-msplt-4848p-f