You guys are missing his first statement...
Apparently Apple pulled the RJ45 from his laptop.
Seriously; invest in a old laptop just to have kicking around.
You can grab old Dell/HP/Whatever notebooks on eBay for under $50. Who cares about battery life, HDD speed, any of that stuff. I buy one every few years to use as a reference PC in my garage to pull up PDFs/Websites/etc while working on my old cars. If I break it, or the weather gets to it? Meh. Buy another. Donate to a school who fixes laptops locally.
I never understand why manufacturers pull basic ports (like that) from a computer. If you bought a new router, for example, how would one configure it, set firewall rules, DHCP settings, static IPs for the router, etc without first configuring it, via a wire, or a million and one other things....