二つ is pretty much always acceptable for counting things, but I would take any individual Japanese person’s perspective on what is or isn’t common with a grain of salt. Things can be regional, and beyond that… they’re just one person.
Presumably, the thing omitted with the が construction would be something like ほしい… but I could be wrong. It seems like an odd way to order. It’s a perfectly fine way to count, but an odd way to order, to my ears.