I'm using one of these https://www.radioddity.com/collections/accessories-earpieces-mic-speaker/products/radioddity-cb-mobile-radio-external-speaker which I bought on sale a while ago. They are not as good as a proper 2.5" communications speaker, bit it's fine for CW, is only 4 ohms impedance and has plenty of drive from my QCX+. Only issue is that they have a mono plug so I knocked together an adapter with volume pot.

73 Andy Gi0VGV