Is There Such a Thing as an Overnight Diaper Size 6 or Higher?

Yes, on the Huggies Overnight Diapers that you have been using. I have bought them at Dominick's, KMart and Target in a 6. If your store doesn't have them, ask the manager to order you some, or go to Diapers.com where you can order them to be delivered right to your house.

I think Pampers Easy Ups come in a 7 and they are designed for both day and nighttime use. I don't use a 7 but I think I saw them in that size once at WalMart in Niles. Also Huggies Pull Ups come in a 2T/3T OR a 4T/5T size, which is pretty large, and they are available in a nighttime absorbency. My 3 year old uses the Huggies Overnight Diapers for bed and underwear during the day, but if we're traveling, I buy whatever I can find, so I have tried all of these things at some point!

We used to buy Huggies Overnights in 6 but my store stopped selling them. My 3 year old is now wearing the s/m size of the Goodnights (i think, they're called) The ones for bedwetters. They are made like pullups and although they are a bit too big on my son, we haven't had any wet beds since we started using them.

Goodnights are pullup-style. They go up to 100 lbs or something, and they hold a lot of liquid. You can buy them most places where diapers are sold - Jewel, Walgreens, Target, etc. carry them.