An alternative to buying flux for all your electronics soldering needs can be made very cheaply and easily ay home.
There are only two items required to make a home made flux alternative.
- Crystallized Colophony rosin, you will be able to find in outdoors, sports and fitness stores, hardware and music stores. It has uses such as for grip assistance in climbing and violin bows.
You can get some here: https://amzn.to/3pQ0ZD7

- A Solvent, this could be isopropyl alcohol or even rubbing alcohol. You can also use acetone or nail polish remover.
You can get some here: https://amzn.to/3pQ0ZD7

Just Mix the colophony rosin and solvent together in a 50/50 ratio. Leave for a while for the rosin to disolve in the solvent.
Once it has disolved just put the resulting liquid in a small plastic bottle and use it as flux when needed.
You can get them here: https://amzn.to/2MwgNwt

Alternativly you can just buy flux cheaply from online stores such as amazon.
Get Some here: https://amzn.to/2XqJNs1