Lost leads (no not for my dog ;)

[#1]

S-i-L has offered me his old Router, I think its is a wired  NetGear 834, but at moment cannot find the leads that go with it. I know you can buy cheap leads, but want to be assured that what I buy is up to the job. Where do I go, as I don't want a telephone lead that is full of bell wire as opposed to the proper stuff. Or should I, in the event he cannot find the original leads, reform from my tight-wadness and buy new hardware?

[#2]

Believe it or not, B&Q Warehouse have decent networking stuff now.  You can also get decent phone line and ethernet cables at PCWorld (you may pay a bit more there though) or your local PC store may have them.
OTOH you could buy this from Amazon.