I'd rather get some posterboard, velcro and markers and make my own. You could get it laminated or just remake the pieces if they get wet/dirty. (Laminate it before the velcro, though.) When I was teaching, I always preferred to be able to have things like that arranged the way I wanted, kwim?
Incidentally, I also think the whole "this is the date, but we're not going to show it on the calendar" thing is pretty advanced. I mean, calendars at all are pretty advanced, but at least with one that has all the days in a month (or, for little guys, just one week), you can do things like write down when some exciting thing will happen, then check off the days with your child and show them how the exciting thing is getting closer. Plus, I always liked to have cards with the numbers 1-31, with a picture on each card, so that as you put them on the calendar each day, it made a pattern that the kids could read and eventually predict (like "snowman, snowman, mitten, snowman, snowman, mitten"). That way, there's really a wide range of activities and concept levels, ranging from understanding the calendar (*very* high level) to "can you find a snowman?" (significantly younger-level skill).