So I thought, why not, opened the router,and lo and behold, the DC circuit is perfectly happy with 5V and 1.2A or so, and converts it down to I believe 3.3V.
So I drilled a hole in the router and soldered the working end of the damaged cable to the power input. Other end is pluggend into the useless USB TV port. Has been working fine ever since. Neither TV nor router runs hot, which I couldn't say about the old wall wart.
In theory, USB should negotiate the required amount of power It turns out the TV manufacturer decided to simply wire the port directly to the internal 5V rail connected to both USB ports, so it should be able to give at least 2x2A.
Yeah, it was probably cheaper to just buy a new router. Got a bit nerd-sniped there I guess ;-) .