the peewees of subsect. Limbatulate…and in sect. Phalloideae.
Spore shape may help a bit. Have any of the specimens been mature enough to produce spores? Have you tried wrapping a stipe base in moist paper towels or cloth and setting the specimen upright in a coffee cup and, then, covering it with something like a tent of waxed paper to try to reduce evaporation (a wad of damp cotton or tissue on the top of the cap can also help keep the moisture in)?
You might be able to get immature material to reach sporulation that way. I’ve succeeded quite a few times … with species in all seven sections. Then you could check out the spores. The Q values can be quite high a few of the white Phalloideae and a relatively larger number of the Limbatulae. You might catch a break. :-)