Yeah, I don't really want to buy kit that I'm only going to use once. So if I can borrow, sweet. or at least if I buy, the least stuff possible so no pre-amps, etc. I'll keep adding stuff to the room anyway so now's not the time to bother too much with measuring.
Behringer does a cheap one, few others in the same price bracket as well. See e.g.
https://www.thomann.de/gb/microphones_for_measurements.html
Note that you'll probably need a mic pre-amp with phantom power for these.