I gave up looking for a seat to go on the full suss and whacked a hamax siesta on the back on the girlfriends old hardtail.
Little Scaled loves it and it’s been good from when she was ~1 to now and looks good until she hits the weight limit, she’s only 2 now but the size of a 3 year old so it might not be that long!
We’ve done a few 25-30 mile rides when we were away on holiday and she was fine with that, few pub stops on the way for drinks/lunch.
It’s been used all summer for taking her to/from the childminder. Best bit of having it on the ‘spare’ bike is that we can just leave it on there and wheel it out without all the faff in the morning where every seconds counts!