hard to get; difficult to obtain
Used for items that are scarce, out of stock, or otherwise not easily acquired. Often seen in product descriptions or news about limited releases.
This limited edition has become hard to get.
I'm looking for a part that is difficult to obtain.
入手 is the act of obtaining; 入手困難 describes the state of being hard to obtain.
困難 is a general term for difficulty; 入手困難 specifically refers to difficulty in obtaining something.
Compound of 入手 (obtaining) and 困難 (difficulty).