Yep, that's exactly what I was going to say,
grab the perlite... it's in the same ballpark,
light airy texture, and has small traces of nutrients..
And just an FYI, when using Perlite vs. Vermiculite..
The perlite is used to keep the soil light and fluffy,
The other does the fluffy part, but also has nutrients in it, but they stay wetter longer and for some plants/
seedlings, it is not nessessary or wanted by some plants that like dry feet/roots...