It only cost me 24p (UK) per antenna for this project, so it is nice and cheap.
My router is a Tenda model, which already has 2 aerials and a dish and only cost me £25, so I would really recommend it.
Step 1: Materials
A Wire Skimmer (for taking food out of pans)
Spare Aerial or stick the same diameter as your aerial
Any other metal strainer/sieve should work to :)
Step 2: Removing the Handle
Do as many as you need, some routers have 3 or more, so make sure you have enough
Step 3: Attaching to the Aerial
If there is no wire to attach to, you can either use hot-melt glue to attach the dish, although you can't take it off or reposition it; or you can attach extra wire to the dish (maybe with glue again) and then bend those into shape.
Make sure the aerial do not slip, as reception could drop annoyingly.
Step 4: Finished