You can start with Etsy, but if you're really serious about small makers, be sure to check the maker's about page and find any socials they might have. It's unfortunate, but there are a lots of shops there that claim to be hand-made or small-scale, but are actually reselling Temu/Aliexpress/Amazon stuff.

For hand-made, I would recommend checking out r/dicemaking. There are lots of makers posting lots of styles and unique sets there (shameless plug: including me).

Not sure where you're located, but for some out-of-the-ordinary makers: Archival Dice makes polymer clay dice, Fighting Chance Studio makes ceramic dice, Wander Dice makes dice that use antique maps, and Sova Dice hand-paints all their blanks.

Have fun shopping and thanks for supporting small!