You can always go wireless, if that isn't an option i would suggest buying a 10 port switch to increase the amount of Ethernet ports you have access to.

Buy a switch. I doubt you'll need a 10 port switch, I have a 5 port which was enough, until I lost its power cable. I bought an 8 port switch on deal and I have 4 ports unused at the moment. Of course, it depends on how many you'll use, but the majority of the time, a 5 port switch would suffice.

Something like this;
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Although, I don't know if I'd be comfortable with that specific one.

If you have an old router lying around you might be able to convert it into a switch using a 3rd party software called DD-WRT. I did that with an old TP-Link router I had and never given me any issues.

Just be warned you can brick your old router during the firmware flashing so just make sure it is of no use at all before doing so. Your main router will not be effected in anyway if the old one does happen to fail and become bricked.