buy it preowned at game stop for around 8 dollars.
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Sonic Adventure 2 Battle can sometimes be found in the used games section of Gamespot for really cheap. The original DC version is no longer for sale. You can probably find both versions on eBay.I bought the Sonic Adventure 2 battle version on eBay this January, the Dreamcast version was there too, but it was a while ago.
it doesn't exist
Ebay
yes you can find it in many levels
you can find them in Pumpkin hill
Aquatic Mine and Iron Gate
I believe sonic and tails can get bears in final rush for sonic for tails im not sure.
Actually there is a way to hack sonic adventure 2 battle and play as super sonic in normal levels just look around the internet and im sure you will find your answer.
Find a fish and use final slash on it.
There are goggles but their not called goggles, they are called sunglasses.
Find a mystic melody (usually in mission 3) and you can use it.