Where can I buy a clip for a Browning 9mm semi-auto 73C77738?

Let's use the correct term- magazine (since that is how they are listed) If your Browning is the Bowning Hi-Power, these are fairly plentiful. Any gun shop should have, or can order for you. You may also order yourself from on line sources. Among many of those is gunpartscorp.com. SOME localities will require that your magzines be limited to 10 rounds- the originals are 13 rounds.