Here's one brand of DIY spray foam:
https://tigerfoam.com/sprayfoaminsulation/
I think it becomes pretty expensive if you're going to try to do an entire house with the stuff, it's better for sealing in limited areas and around the edges of doors and windows, etc.
Vermiculite is actually a very good insulator but as you said it tends to sag and compact in the wall cavities (you will have to get it out of there if you're going to replace it with something else.)
Blown in cellulose insulation may be a better solution, it insulates well and is pretty inexpensive compared to other methods. It can be a DIY project as well, most big box stores will rent you the blower required for installing it.