There exist investment firms where some measure of return to society is incorporated into investment decisions (see e.g. https://acumen.org/). If your business is creating some sort of positive externality, then seeking these sorts of investors (whose problem interests are aligned with your company's) may be a good fit.
It sounds like what you actually want to do, however, is just create a vanilla business and put a cap on what is returned to investors. You can do this -- in fact, you can do whatever you want, the world is your oyster. The only question is if anyone will invest. VCs who want an unbounded or very large upside won't, but there exist investors who will probably waive the right to any unlikely windfalls for more certainty of low-level gains. See e.g. https://earnestcapital.com/about/.
I believe you will not find this with classic VCs. I would attempt to look for funding with sources that support NGOs and other social enterprises.
Short notice? well...good luck
>How I could find in a short notice this kind of sources of investment? I don't live in a country where there's an abundance of investors, let alone "socially responsible investors".
Congratulations for product market fit. Have you considered debt and going to banks? There may also be organizations, either governmental or not, that promote entrepreneurship/startups/small businesses.
I guess the first question you want to answer, is to define which kind of company you want to build ?
As a founder, as you say, you want to optimize the impact of your company. I am not sure what you mean by traditional companies, but startups are not about maximizing profit. At least not in the short term.
VCs are looking at maximizing their returns on investement when the company exits, not based on dividends.
If you don't want create a startup, but what I would call a traditional company, ie not looking for hypergrowth, but that your company is profitable, then lots of people are probably willing to invest in it.