need a range extender for -

[Ghost in the Shell]

my parents wireless setup. they have one wired and one wireless device both fine but the furthest wireless device is not getting a signal. the kit they have is the DLINK DSL 904 - which provides an ADSL modem and a USB network adapter

now they just need a range extender thats fully compatiable

would somebody be kind enough to suggest such a thing and try to keep the $ low if possible

thanks