Here's a natural minor in A on Amazon:

https://www.amazon.com/SEYDEL-Session-Steel-Natural-Harmonica/dp/B01DBWYT8W/ref=sr_1_8?s=musical-instruments&ie=UTF8&qid=1475784072&sr=1-8&keywords=harmonica+seydel+natural+minor

A decent chromatic harmonica will run you about $130 for a cheaper one, $200 and up for a nice one. They are also more difficult to play with a much bigger learning curve, though you can play in any key, no re-tuning needed. Anything less than $100 for a chromatic is valveless and probably junk.

I would suggest starting simple to see if it's going to be your thing.