In addition to the bullets, stem microphones, usually vocal microphones, are used, especially if the sound should be more acoustic. Modern vocal microphones are usually "low impedance" and have a symmetrical XLR connection. But by Gussow we have already learned that there are still old, "high-impedance" microphones. On the market, still two models from Shure are available, the Unisphere models, the SD 545 (predecessor of the SM57) and the SD 565 (predecessor of the SM58).
In the picture a Shure SD 565, already in use at Woodstock, so it looks at least. To simplify the cupping, you can remove the basket and build up a funnel for yourself. However, it is a great advantage when you have access to a CNC lathe. DIY is required, see below.
Problem USA XLR
Such a micro is expensive so you look on ebay. If these microphones from the United States, a strange phenomenon shows up. LowZ, HighZ does not work. Therefore, the microphone is not broken, it is like with the Hohner Bluesblaster the connector pin assignment. The first picture shows the state of the United States. The black cable must go to the blue cable. Then it works, see second image. In the third picture, a snippet (source: Shure). The orange line is to show how the United States version is wired.
SM57 and copies
The SM 57 and also some copies of it are suitable as microphones for harmonica. You want the bullet sound, an impedance transformer is recommended. This one can be installed inside the microphone or plugged in between as an adapter.
There's only one problem. The basket produces noises, if you hold it in your hand. Greg Heumann has a funnel, which is fixed with Allen screws. My funnel just holds due to the friction of the rubber rings in the fit. Proven. Many funnels lead to the Shure!