The HydraBlu Versa Flow looks virtually identical to the Sawyer Mini, just made with white plastic ends instead of black, and with a different brand name and info printed on the label, so I would guess that is it simply a cheap Chinese knock off copy of the Mini, perhaps even coming out of the same factory. The Chinese copy stuff all the time, even if it is illegal for them to do, as they simply ignore patents on things. Interestingly, I weighed my Sawyer Mini and it weighs 1.3oz...0.1oz lighter than the Versa flow, so I will stick with my Sawyer. Here is an interesting video showing an Activated Charcoal Filter hack for both the Sawyer Mini and the Squeeze. He has a second video showing how to make your own.
https://www.youtube.com/watch?v=iZizSOi7wmg
The problem with his hack, whilst quite cleverly though out, is that it involves PVC tubing, and Expoxy adhesive, which are both potentially toxic (that is why they don't use PVC in domestic water supply tubing, and why it's only used to carry waste water), and PVC can also give water a nasty "plasticy" taste too. Domestic water supply tubing is usually non toxic MDPE (Medium Density Polyethylene). This is why I am waiting for my Sawyer adapters to arrive before I attempt to make my own ACF, and I plan to use non toxic plastics instead.