You need this:
Ensure you get the V.2 OR V.3 because they have the reapeter mode you need. Many routers dont have this, so be careful selecting.
This is the reason I suggest the Netgear, it's the same brand and has the repeating feature.
Try click here
UK site, and use QuickFind code 46057 in the search box.
It's £49.73 inc VAT here, and used from £30.04
I think thats the V.3, or should be anyway. Update firmware before use though.