The Niagara is a good choice if it's still under $30 on Aliexpress and the smallest dual battery squonk mod I know of AND will fit in trouser pockets, as much as I love the Topside the Drone BF DNA is an absolute steal for a DNA mod, I'm gutted as I'm spent out so can't grab this offer.
DNA colour are most definitely worth the money, the chipset alone is over 50 quid and it's customisation is the best on any mod I've owned (I have the DNA75c in a Therion but it's pretty much the same).
To answer your question about the weight of the Topside, yes it's quite heavy and all though it's not 'pocket friendly' I still manage it and take it out a lot in my jacket pocket, for the brief summer period we might get I will probably shove it in a waist pouch even though I hate them.
There's plenty of single battery squonkers if weight is an issue but I would go for a dual if you're out and about a lot.
Good luck on your shopping quest, but I would snatch the Drone if it was me.