I really do not want to carry around one of those extra blue tanks on wheels if at all possible....
Our TT only has a 30 gal. gray & 30 gal. black. When we camp at electric-only state park sites we bring a 42 gallon Barker Waste Tote. It can be connected to the TV hitch and towed to the CG dumpsite. Since it's just gray, we don't have to dump it right away & this allows our family of 5 to take decent showers (w/the Oxigenics shower head) for a few days between dumping.
Also, we have a 48 gallon FW bladder that I place on top of our fiberglass cap & fill-up from the main CG spigot. It fills our 42 gallon FW tank so we don't have to worry about making a bunch of trips w/smaller 5 gallon containers, etc.
It's all good. We have a roomy 2-slide TT w/3 separate rooms, outdoor kitchen, etc. that weighs less than 6,500 (empty). If they kept adding this & that it would weight a lot more...