@rastavape: Elemental Wellness and San Jose Patient's Group carries cartridges. Harborside SJ carries the omicrons, but does not sell spare carts.
@mephisto: That's exactly how I used to scrape the final bits out of the vial - I set the solo on 2-3, opened the cap, and set the vial in the solo's bowl. Got it liquidy enough to scrape/pour out.
On a semi related note, the bent glass stems with their bend angle work perfectly to reclaim oil from a dead cart - put a cart in the bowl end of the elbow, and you can heat it up as hot as you need without having to hold really hot metal.
I have a stem where the mouthpiece broke slightly, so I put the cart in there upside down and when heated, it pours all of its oil out into the glass which collects on top of the holes. I replace cart with a new one, then heat the bowl end of the stem to flow the oil back into the new cart.