We are full-timers and only going to CG with sewer hookups would force use to miss many great CG/ locations.
Out of the last 451 nights camping - 117 of those have been at locations without a sewer connection. The most common place we camp without a sewer connection is also the place we stay longest at any one time - the COE campground nearest our children/ grandchildren. Tends to be 2-4 weeks twice a year. We can usually go 7 days on the grey tank, and 10 days on the black tank.
We really don't like to pull-in the slides - undo the manual leveling - and pull the rig to the dump station. Go back re-level, redeploy the slides, etc.
So I have a 27 gal Thetford.
#1 - will never buy a Thetford again - will go with Barker. They dump much better. I've replaced wheels on the caster and the rear so that it tows much better than original. I would also replace wheels on a Barker.
#2 - an almost full 27 gal is about all the weight I can handle. A couple times I've had to hook a tow rope up to the truck and the handle to get it from the dump side of the TT to the road.
#3 - I never allow the sewer tote to get completely full. I have 72 gal of black and grey capacity. Sometimes I need to make three trips to the DS. Still less time and hassle than unhooking and re-setting up the TT. I usually fill the sewer tote about 1/2 full from the black tank, then almost 1/2 full from the grey tank. It's easy to estimate how full the tote is when you use it fairly often.
#4 - Always wash out the sewer tote at the DS. After I've finished dumping - I always put a little of my toilet chemical in the sewer tote.
# 5 - wish list
1) - Class A with automatic leveling system - then I would drive over to the DS.
2) - Macerator - put the tote in the truck - fill it with the macerator and drain it easier.
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For the OP - what you want is a 60-100 gal collapsible tank, and a macerator pump. Put the collapsible tank in the bed of the pickup and fill it with a macerator pump.
Hard sided tankPillow tank