Matt,do be careful with that chuck. Those special Jacobs with the safety collar are rather rare,and cost a good bit if you buy them new. It might cost more than your drill press did.
And now,Jacobs are made in China. The new ones might not be very good.
I am wondering if it would be possible to take a SIMILAR 1/2" Jacobs chuck without the collar,and just fit your collar parts to it? I have no idea if the bodies would be the same,but just without the collar.
Now that you have the collet chuck though,it is not really a necessity to have the locking collar on your chuck. You shouldn't be putting sideways pressure on it to make it come loose from the #33 taper. You could just get a regular 1/2" chuck that is more common,with the 33 taper hole in the top,and use that,if worse comes to worse. And,try to buy an old MADE IN USA Jacobs in good shape. I can't advise buying a Chinese Jacobs. I just do not know if they are good or not. Perhaps Jacobs has them made to the proper tolerances,and of GOOD metal. I have no idea.