This is old but it might help someone I think.
Solution #1 Free!!! Well, kind of...
Should you have any old laptop with wireless working not being used around your house you can run OSX, Linux or Windows and share the laptop wireless through the ethernet port of the laptop.
Solution #2 Very affordable
See if you have a router you are not using any longer and if it supports wireless extender functions or see if you can flash its firmware with DD-WRT or other third party firmware and put the router in client bridge or wireless repeater mode. Depending on what mode you choose you will be able to have the first router to DHCP all the machines attached to the second router so that all of them stay on the same subnet.