Raw sewage, on average, weighs ~9 Lbs a gallon - so that carrier will weigh 135 LBS + the weight of the carrier. Make sure it has wheels and some way to attach it to your TV.
DANGER DANGER WILL ROBINSON!!
You have a 40 Gal holding tank? a 40 Gal Grey Water tank?
If it were me, I would get the shortest sewer hose I could find to hook your RV to this *tiny* 15 Gal dump tank.
Why? Cuz when you open the valve in the black tank, it's gonna GUSH fast, and you are gonna want to flush that hose with grey water. If you are using a typical 10-15' long sewer that sucker could over fill your portable holding tank REAL fast
Not trying to disuade you, just giving you food for thought to prevent a possible black water campground disaster...