50 is a small number, your best bet is to traverse a number of chip plants to get what you need.
There's a handy tool that lets you find places that sells them. Look for the sectors with 2 chip plants and just camp out there, make sure those factories are fully stocked on the resources.
Rather than camping out in your own ship, you can just buy a freighter and order them to dock at the chip plants. As long as you have the trading system extension on your ship you can purchase/sell items remotely.
Later on, when you have to gather 50000(!!!) microchips for your hub mission, your best bet then is to produce some massive micro chip complexes (they make a lot of money as well after your mission is done).