I love Goodnites, they are the diapers I use the most. I've found that baby diaper boosters fit pretty well in them, since that's the size of diaper they were designed for and they even advertise them for use in baby diapers and training pants and bedwetting pants.
The main brand is Sposie I believe, they have a number of sizes. The 4-6 and 3T-5T are the same dimensions, but the T one is slightly more absorbent and has an adhesive strip if that's your preference; I have used the 3T-5T and it works quite well in my Goodnites, I think it basically doubles the capacity.
They also have the
Super Sposie, which is longer, wider, and has higher capacity; it's advertised for youth and young adult diapers. I've tried super sposies in Goodnites, their length covers the whole length of the inside of the diaper. But I've found when I put it in a dry Goodnites, it can cause leaks over the leg guards before the Goodnite is fully wet if you're not careful with how fast you wet it, so the flow through isn't perfect. Another way I have used them is wetting my Goodnite and then adding the booster so I can continue using it, I've found this way is better to fully use both the Goodnite and the booster, and I think it doesn't leak as quickly, but when it does it's still over the leg guards. I'm realizing now that maybe these super sposies weren't designed for Goodnites, but instead tape-on youth and young adult diapers, which would probably be wider and have higher leg guards.
ABDL boosters would probably be too wide and thick for Goodnites, although I haven't tried them.