I am interested too. I want a fully submergable for 10 gallons of water, that I can connect hoses to for in/out and either bury in stone or box in with slate. ideally, I'd have to remove the filter INFREQUENTLY.
It needs to be internal because the tank is in a little nitch where there is no room on the sides or the back to hang on a filter, hence the need for an internal one.