Did you search online for bulb vendors? I saw Brecks.com has some.

Try here: https://sweetdreamamaryllis.com. Most larger bulb vendors will offer a reasonable selection as well.

Keep in mind this is sort of the off season for amaryllis and many varieties are currently sold out. Stock might be more widely available later in the year.

Easy to Grow Bulbs is a well known reseller in the United States. https://www.easytogrowbulbs.com/collections/amaryllis

Where do they grow these "Amarylis"? There is obviously an established supply chain, do most come from the same place?. How do they get them ready for forcing?

Look for independent growers like that Sweat Dream company for something different., and apparently they keep them in soil.

Dutchgrown.com Best Amaryllis i have ever bought. Expensive but totally worth it! Buy the jumbo size. Got 3 bloom stalks from every one of these bulbs!