They used to be in schools across the USA, and to a lesser extent in homes in Performa guise.
There are some reasons you won't find these as much anymore:
1. Schools tended to recycle these things en masse in the early to mid 2000s.
2. The ones that didn't get recycled were often stripped for their boards in the late 1990s-early 2000s, since people would hotrod CCs with them.
3. "Spindler Plastic". The plastic of these computers has become so brittle that many fell apart in transit, storage, or shipping.
They're not as rare as some of the lesser-known models, but they aren't as plentiful as, say, the SE. Try to find one locally, since shipping these things is going to be more trouble than it's worth. You never know when they'll come out of hiding; I found an LC 550 on Craigslist (the rare no-CD ROM model) two years ago. It was owned by an older lady who rarely used it and had bought it through the school she used to work at when it was new. Later that year, I also came across a Performa 575. It had a similar story in the fact it was rarely used, although this one wasn't found on Craigslist; it was offered to me by her son, who happens to be my pastor!