I have about a 500ml bottle of flux and I refill a paintbrush pen using a disposable pipette. Works fine as long as you do not put the nylon brush on anything hot. Probably exactly like your Hakko pen without the logo and price!
They are not. The Hakko (which is a rebadged Bonkote Bon Pen) has a valve inside, which those watercolor brushes lack.
Also, the watercolor brushes don’t always hold up to the solvents in flux. I tried (even good quality name brand) watercolor brushes and they became leaky fairly quickly. Additionally, they aren’t ESD-safe.
Looks like similar thing here for $2: https://www.aliexpress.us/item/3256806458874298.html
Thanks, that looks nearly identical to the hakko!
The counterfeit Bonkote pens have a terrible reputation, becoming leaky much faster than the real ones, and not dosing the liquid well.
See also:
https://www.bonkote.co.jp/en/bonpenand
https://www.bonkote.co.jp/en/counterfeit-goodsP.S. I have a strong suspicion that the actual physical manufacturer of the Bon Pen is Pentel, since they look identical to the Pentel Art Brush/Color Brush/Colour Brush, but with customized tips and ESD-safe materials tested to withstand solvents.