I’m a big fan of 10mm, so will always champion that as a scale choice. If you already have terrain in 10mm (and have ECW figures) then it would seem sensible to stick with this.
Pendraken are a good choice, and have added some more codes into their Renaissance ranges recently - whilst they are not specifically eastern ones, they may work.
Warmonger miniatures in the USA have some very nice Landsnecknets if these fit in era wise?
New Line miniatures and Lancashire games are worth a look