Might be too late by now, but I have a mono filio and it works well. It’s one of two glass teapots(which I know of) that are 100% plastic free while also having a large infuser basket. The other one is the Bodum Chambord(specifically the glass-and-stainless-steel version), which might be even better because of how the basket is constructed(that is, it might let fewer little bits pass through), but I don’t have any personal experience to confirm or deny that. As far as I know, either one would just fit into your budget.

And yeah, I know that if you ignore the size of their filter/infuser baskets, there are plenty of other plastic-free glass teapots. But my recommendation would be to get one with a large infuser basket, and afaik that’s only those two.