Neotori is my go-to. Their Mundir wolf model is fantastic, the Theotolax is a close second. They have a decent selection of knotted toys, so take a look around.
Prices are good, they're based in Germany and they have reasonably good international shipping. They do weekly premade and flop drops every other Friday if you want a discount.
Their "soft" option is great for knotting; they do mean very soft, it's surprisingly squishy. Durability is excellent too, my first toy from them is still in perfect condition five years later.
Size wise the beginner and small were manageable with little to no stretching, but size escalates VERY quickly after that. That's my one criticism but some people are into that.
Honorable mention to Primal Hardwere and BD (as usual).
