So I’ve got my lovely little IWC Small Da Vinci with a whopping diameter of 29mm. I love it. And yeah, I do actually rely on the moonphase for keeping track of a certain something that comes around every 28 days.
Here’s a crappy cell phone picture of the IWC on my wrist:

IWC Small Da Vinci on a 5.5" wrist, worn slightly higher than I'd prefer as the strap is the tiniest bit too loose
More small moonphases I hope to own someday:
- Zenith Elite Ultra Thin Lady Moonphase – 33mm, Elite 692 Automatic movement… (Not sure which model I like most out of the three stainless steel choices. Maybe I should get the one completely encrusted with diamonds*? Haha.)
- Blancpain Léman Complete Calendar – 34mm, 6763 movement
- Oris Artelier Complication – 35mm (also comes in 40mm), Oris 581 base ETA 2688/2671 movement
- Jaeger-LeCoultre Master Ultra Thin Moon 39 – 39mm (probably too big for me, but the thinness may make it doable), JLC 925 movement
*I really hate diamonds. If it weren’t for the fact that all the Patek Philippe ladies moonphases have that nonsense all over the case, it would probably be on my list as an unattainable grail. Oh well, one less expensive thing to covet.