how to buy power cords that fit my components (i.e tight and snug)

I've seen people change out the female socket in their component to tighten it up.

Manufacturers are generally not going to make it tight unless they are selling both halves and even then they will give plenty of clearance.  Won't fit in the hole is a sure way to get a sale returned.

Frankly, I'm not sure what you are concerned about.   Is the wire sagging a big as it comes out of the component?  I don't think there is any concern about the electrical connection.

Jerry

Use electrical tape.

Trial and error.

I think Synergistics makes little pieces that go around the cables to tighten them up.  If not them, I know there are others who do.  My buddy just got a few of them for the same reason.  Little film pieces molded to go around the cable ends.

Rather than focus on what will not improve sound, and maybe make things worse, why not address the root cause of the problem? Support power cords so they naturally lay where you want them to be. That way not only is there no stress on the connection, but when properly supported there is much less vibration in the cord, and far less being fed into the component by the cord. Until and unless this is done then making the plug fit even tighter is making things worse not better.