ASIC Bitcoin mining chip
I think the phrasing of the question shows some confusion over what an ASIC is. ASIC means Application Specific Integrated Circuit. It is application specific: the chip is designed for one specific application. If you want to mine Bitcoin, you design an ASIC whose application is mining Bitcoin (or, probably, computing SHA256 hashes as fast as possible, which is the computationally demanding part of mining Bitcoin). The hardware is designed to do that, and only that; it will never be able to do anything else. That's what makes it so efficient at mining Bitcoin.
So you nobody just buys “ASIC chips” and turn them into Bitcoin miners. If you are an end user (miner) you buy Bitcoin mining equipment (computer components) that contain ASICs designed to mine Bitcoin. If you are a Bitcoin mining equipment manufacturer, you design chips (ASICs) specifically dedicated to mining Bitcoin, have them manufactured by a foundry, integrate them with some other electronics to make it talk to the computer, and sell it to miners.
Getting the raw Bitcoin mining ASIC chips and building your own devices out of them is probably close to impossible, and useless since the really interesting technology is the design and the implementation of the ASIC chip and not the cheap electronics around.