We had a Coleman Sequoia popup for 20 years. We used the 5 gal Barker as in the link in the post above (handle, no wheels). Pretty easy to carry, usually emptied every other day (2 kids, one DW). Kept it clean on the outside so it travelled under the dinette table. You can empty at the dump station or right into the toilet at the bath house.
Easier to dump than the porta-potty.
1988 Coleman Sequoia - popup (1987-2009) - outlasted 3 Dodge Grand Caravans!
2012 Roo19 - hybrid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado 1500 Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10