Hi John - have you looked online? I’d expect a number of bonsai nurseries have young maples as well as low, glazed pots. And depending on how much work you want to put into the trees, starting with nursery material or even some seeds or seedlings could add to the mix.
Midwest Bonsai Society lists a few local nurseries: http://www.midwestbonsai.org/chiresources.html. I’d check non-bonsai nurseries too.
I bought most of the trees in the post (http://bonsaitonight.com/2014/02/14/a-japanese-maple-grove/) at a bonsai club sale. They were planted on a rock. I put them into individual containers, pruned them, and waited a year for them to get really healthy. I added in one or two from other sources - including a seedling my mom started - so they’d be different shapes and sizes. I found the pot at Boon’s garden.
I like collecting trees with imperfections as they’re great for forests. And because fewer people are on the lookout for flawed trees they’re often affordable. Plus, developing them can be fun.