Come on… no knock offs!!! They are not classic, not quality, and are a waste of money.
You might be able to find a vintage one though, but vintage Soft Pad chairs usually are around $1500+ Management chairs if fabric and not mint condition might be in the $500 range.
Similar vibe, you can look for a vintage Knoll Pollock Chair, they are usually under 200. I had one as my home office chair for a number of years. You can find them with just a swivel base side chair style, or a tilt and swivel management style. They come in leather, fabric or vinyl.
Another option is too look locally for a used Aeron Chair, if you are looking for more of a task style. Not my personal style, but I know a lot of people like them.
R