Love my Tout-terrain Streamliner
We have the Tout-Terrrain Streamliner. The US importer is Peter Whyte Cycles. He doesn't list it on his website. We got our Singletrailer from him, not the greatest company to work with.
I got mine slightly used in Holland.
If you live in North America and are traveling to Europe, the exchange rate is pretty good right now and remember, the prices include ~20% tax, which you could get refunded if you ask beforehand. All in all it wasn't cheap but far less than people spend on their own bikes.
I took it apart and it fit inside our fairly normal suitcase.
Having suspension is great. I don't ride over crazy stuff, but the usual roots and small rocks that disappear under a 26" or 29" adult wheel with an aware rider are very different for a kid on a 20" wheel who can't see them coming.
With the suspension on the tag-along I feel fine cruising at speed through root sections and small rocks, <3". If my child was on a rigid tag-along they would get so rattled and bucked it wouldn't be rideable, until you slowed down to a crawling pace.
My 4 yr old daughter also is still working on learning to stand on the pedals and keep her feet on them, less bounce is definitely a good thing. Fat tires are good, but since they don't have rebound damping they bounce back up afterwards.
Unfortunately it doesn't fit on a 29er for off-road use. I had a new tube welded into the pulling arm to lengthen it and increase tire clearance. This might also be an issue for very short people riding a 26" with a dropper post.
The wheelbase is long, so you have to ride very wide on corners. This makes the ladder bridges on our local trails difficult as well as tight corners around trees. But as far as riding over bumpy stuff you can ride anything you'd feel safe riding with your child.
