Hello, couldn't find any posts with this. You can use other silicone bottles with the gbox. I did it today with an 8ml generic bottle I got off Ebay. IMO it makes squonking and refilling with a refill bottle much easier. Here are some links. One of the methods does require taking off the back panel which are #6 torx screws, and removing the metal tube assembly, quite easy though.
Credit to mike vapes and the community on reddit.
https://www.reddit.com/r/electronic_cigarette/comments/821b75/gbox_squonk_bottle_hack/
Credit to mike vapes and the community on reddit.