Luke Winship :
2nd option seems most viable, we will have to go out to by the stuff needed but feel free to post the steps and I can come back to this when I get them, cheers!
To start, get 225-275ft CAT5e Ethernet cable with RJ-45 terminals. Measure from the main router to the location where the second router will be placed.
You could get Cat5e outdoor waterproof Ethernet cable. Otherwise, you will need around 21 3/4" x 10' PVC pipes, and fittings (couplings and elbows) to connect them depending of the layout. If you find belled pipes, where one end fits into the next pipe, you could save on fittings.
Get the cheapest PVC with the lowest PSI rating, since there is not pressure requirements. It should cost $2.50 or less per 10' feet pipe.
Also get cement and primer to seal the joints to prevent water and soil getting into the pipe. After you are done installing the pipe and wire, seal each end with silicone to prevent bugs, water, moisture entering the pipe.