There are several Flash enabled browsers. They all work similarly to Puffin, in that they actually run the site on a remote server and re-display the content to the iPad.
Just search for Flash Browser in the app store. One or two of them are free. but I've yet to see a free Flash browser that was any good. If it's important to you, pony up the cost of the browser. Developers need to make a living too.
I like Puffin, mostly because it's versatile control options; important if you're going to Flash sites that have non-standard controls, or are games. I understand Photon is pretty good too.
Read the descriptions carefully. Some browsers with Flash in their name aren't Flash capable.
Note: Because Flash browsers have to run on a remote server, there are some privacy concerns. Another reason to pick a more reputable app and developer. Even then, I wouldn't use make any sensitive or financial transactions in a Flash browser on iOS.