I’ve gotten many of these in the past. Both our children have them for the first anniversary of their Baptism. My wife and I have one from our wedding as our college friend who was studying at the seminary in Rome at the time gave it to us as a wedding present. I’ve also gotten them for the First Communion of my godchildren.
In general, you can get them for any sacrament or any significant anniversary of a sacrament (1st, 5th, 10th, etc.). There are other occasions, too—such as family blessing, parish blessings, birthdays, etc. When I was ordering them more often (about 10 years ago), you actually could request one for an event that had recently passed (within the last few months). I’m not sure if anything has changed in that regard.
I always got them through the diocesan office. At the time, it was easy for me to do that. They had a booklet to look through to choose a design and size. Note, they do not come in standard U.S. sizes (5x7, 8x10, etc.). It’s all metric.
And yes, it takes several months between the time you request it and the time you receive it. So it’s definitely helpful to plan ahead.