Your audio isn’t what it used to be and its time to replace the mic on your CB but upgrading will mean more choice and quality than the basic mic that you bought with your CB.
The choice of new or used is never an easy one but if you are a purist and want to have the mic to match your CB the age of the set will make that decision for you. The one problem with buying a used mic is they are usually the most handled part of the rig and in between spending years clasped in a sweaty palm and being dropped on a regular basis means some of the used ones up for sale can be in poor condition.
CB Radios have preset limits on the amount of modulation that can be applied to the outgoing radio signal (as do most commercial available two way radios), this is set as a requirement in the type of license issued to make their production and sale possible.
If these limits were not controlled imagine the utter chaos on a channelized system like CB, its bad enough sometimes when another transmitter near by bleeds over 2 channels either side but take away modulation presets and things would be a lot worse.
The only way to remove these preset limits is to physically bypass this circuit inside the CB altogether (but that’s another web page altogether).
When choosing a replacement mic the frequency response is an important factor, not enough response down at the low end of the sound frequency and your voice will lack any bass.
One recommendation if you think that your mic might be letting you down is to borrow one in the short term and compare the audio against the one your are thinking of replacing as your mic may not be the problem and something else could be destroying the audio output of your setup.
Don’t fear the plug!
Even if you cant find what you want in the pin out style for your CB these things can easily be fixed with little knowledge and skill needed to change the plug or the wiring as all mics are of the same basic design.
The internet is full of information about making these changes and any good dealer will have some idea about what you should do to adapt your new mic or at least be able to point you in the right direction.
What ever CB radio you use finding a mic to fit it or adapting another for your rig is easy enough.