Available four chars domains with results in the WayBack Machine

As usual, you can check them even using the domain checker in the right sidebar.
All of them were available at time of posting.

ez-m.net
hkfa.org
clda.net
cnbm.org
ualg.net
czyw.net
b1c1.com
t518.net
vsbf.org
w36w.com
xgan.org