More unobtrusive might be a pair of thin diameter cables, vertical-dropped from the ceiling. After that you have additional options for keeping them in place and angle orienting them as necessary: a spacer bar, or individual mic 'aimers'....eg
https://www.bhphotovideo.com/c/produ...ne_Hanger.html
If there's any aircon in the building it's possible that the mics could move slightly in the airflow, and you may also want to move the mic pair to give coverage of a choir or solo performer...to accomplish this you'll need thin nylon fishing tie lines fixed diagonally along the side walls, to provide anti-sway tension.
These are very standard procedures for suspending mics, and in practice provide the least visible and secure methods for achieving this. Depending upon the natural and artificial lighting involved, a shiny or matte finish on the metal parts may catch the light more or less, so run your own 'visibility experiments': matte black can often draw MORE attention in such cases.
Before committing to any suspension method, do all your mic placement trials for best audio performance using a pair of mic stands (or single stand with spacer bar)
In my experience a 70 cm nickel-finish bar (plus nylon fishing line) gives the best combination of stability and invisibility for a ceiling-suspended pair.