I have been working for over 40 years and I have never given my boss a birthday gift nor was I ever asked to chip in for a birthday gift for any boss nor did I ever witness anyone giving their boss a birthday gift! There are many phrases that describe giving gifts to your boss but I will keep this clean and you can use your own imagination. I really do not think a boss should accept a gift from an employee unless it is a group which includes everyone on the team and it is a special occasion like retirement or promotion.
I am not anti-boss or cheap in any way but it is a bad precedence to set and once you start how will you stop if need be? What if he already has what you gave him? What if he hates what you gave him? What if you insulted him with your gift? What if he decides he is paying you too much? What if he thinks he has to reciprocate with all of you? Yikes!
What I think is appropriate would be a humorous, light hearted Birthday card signed by all; no inside jokes or off color humor-just “Happy Birthday Boss and Many More” then sign your name. Don’t add any closing greeting like” Love” or “See ya later”.