Nice find but $4.99 for black steel is no bargain. I’d pay that for SS.
OEM is black steel and basically same price as the ones I found.
"when dissimilar metals come in contact, the chances of galvanic corrosion arise. The same is the case with aluminum and stainless steel.
Apart from the two dissimilar metals, there is a need for an electrolyte that provides an appropriate environment for galvanic corrosion. In the case of aluminum and stainless steel, the moisture in the air or the water works as an electrolyte."
https://www.metalworkmasters.com/materials/stainless-steel-screws-in-aluminum/