Are there funding sources for open-access fees for an independent researcher in industry? Since I finished graduate school (statistics), I have been pursuing research. This is on my own time, separate from my work in industry, and while my company does not interfere with my work, they give no financial support.

I now want to publish a paper in an open-access journal. (I know to look out for predatory OA journals, and the ones I'm considering definitely are not.) However, the open-access fee comes straight from my pocket and is not a trivial amount of money.

What could an independent researcher like me pursue as a funding source to cover the OA fee? 

I did find this question, but I am interested in the OA fee in particular, not compensation for the work in general (wonderful as that would be).
As a formerly independent researcher I have looked into this matter before; regrettably, the answer is disappointing: Funders usually require an affiliation with a research institution. (Yes, it is paradox that 'open science' generates new exclusions, leaving certain segments of science behind; this entrenchment of new inequalities due to open access-movements was recently called 'academic colonialism', though this term may go too far.)

Anyway, there may be an alternative route. So-called transformative agreements between scholarly publishers and (country-level) consortia allow researchers from all institutions covered by the consortia to publish Open Access (OA) for free.

Now if you are well-connected to researchers at research institutions which are eligible for this waiver of OA publishing charges because they are part of the consortia, then you may ask them whether you can "borrow" their institutional affiliation. That way you would be able to publish OA without any costs. This does succeed sometimes - because research institutions also have an interest in inflating their publication statistics.