no-blue-screen said:
Will any of the A4 rims fit the A5?
No, the bolt patterns are different.
As for a cheap source for rims,
http://wheelcollision.com/ has fairly good prices for refurb'd rims. We ordered a wheel from then a while back for a customer and were surprised at how good the face of the rim looked, brand new (inside of rim wasn't repainted). It cost about half the price from them VS over the counter.
Beyond that, the deals that pop up every so often when little Billy decides to be extra stupid and gets the latest
bling bling wheels he saw in some "tuner" magazine... the ad had a lady with large boobs standing next to the wheels, so the wheels must be cool and Billy is kidding himself if he thinks those
bling bling wheels are going to get him a pair of boobs like that. At best, Billy will get old man boobs later in life... Billy is stupid, so keep your eye out for him.