My phone is my very best fitting aid!
Before I started using my phone on a self timer, I would run across one of those "little bendy things" constantly. Once I wanted one - nowhere to be seen! And do I ever remember to tack it onto an Amazon order - of course not!
I find a piece of furniture or countertop that is 36" high and then I'll place a few books to raise it up another 6" or8". Place a washcloth on that and find something to lean the phone against as upright as possible - the washcloth will prevent it from slipping. If light is poor I position a table lamp, without the shade.
Once you figure out where/how to prop the phone, it's very quick to set up when needed and the results are a thousand times better than anything you can take in a mirror. While mirror photos can give an idea of what a garment looks like, they are virtually useless for determining fit because raised arms are problematic, plus you can't hardly shoot a back view at all.