ValleyViewVapes offers a pyrex tank with a side fill hole for easy filling. But really it will fit in most tanks. Only tank type i'm not sure about is a tank that uses grommets. Someone else will have to chime in about those.
VVV is going to be down for awhile. Ray, the owner, injured his back and has to have surgery.
Grommets you see in some tanks just hold the carto in place, the same way as a cap. Unless a carto tank has a fill hole (side or top), which most don't, they are filled by sliding the carto down and filling the tank from the top. There is a link in my signature to a video about how to do a "Hot Swap" (that's changing carto with liquid still in the tank), if you just look at the first part, where I slide the carto down, that's what you do to fill it - then you just slide it back up into place.