However, there is another thing that troubles me, the use of plastic in my preferred razor.
This is not a problem at all.
Plastic is a chemical that is made from oil.
Oil can be made from trees.
Therefore, plastic can be made from trees too.
Using plastic should not be avoided, you should instead just ensure that (1) you use so little plastic that your share of the trees on this planet is enough to make all plastic you use, and (2) that the plastic is burned to energy at the end of its lifetime to prevent it from getting to the oceans. The important thing here is that the humans on this planet use so little plastic that only few percent of oil consumption is needed to create it. So for example somebody who argues that hey gasoline can be made from trees too so I'll continue driving my gasoline car, is wrong, because gasoline is used in such large quantities that no way could the trees on the planet supply enough oil to create enough gasoline.
Perhaps some very large excessive use of single-use plastic could be avoided, but I'd say 99% of plastic use is not excessive. Also something that 100% certainly distributes microplastics to the environment like a weed whacker with plastic cutting line instead of steel cutting blade can be argued to be bad.
I am aware of stainless steel blades that are cheap that'll go into steel razor slots
You seem to think that steel is somehow better than plastics.
It's not. Like plastics that are made from oil, steel is made from iron ore reduced using coal. So the steel production today is one of the dirtiest things human race does, emitting nearly 10% of the CO2 emissions caused by humans on this planet. I'd say actually that if we compare the emissions of plastic production to the emissions of steel production, it's steel that creates more CO2 emissions than plastics.
Actually if there's some material that's evil, it's concrete. Cement production for making concrete requires a chemical reaction that releases CO2 and there's no way to avoid that CO2 emission because it's part of the reaction. Sure you could capture the CO2 but then there's the question if it's economical to ship it to an area with geological formations that can be used to store CO2 and if the formation is stable enough to retain it for hundreds of millenia. And if we even have enough many such formations to store all CO2 produced by cement making.
Fortunately, like you shouldn't avoid plastics (because they can be made from trees), there's no reason to avoid steel (because iron ore can be reduced using hydrogen created by electrolysis fueled by renewable wind and solar power). Concrete however should probably be avoided if it's an option to use something like wood instead.
Come to think of it, I won't mind spending more for a sustainable alternative with equivalent benefits ?
If you believe that plastic should be made sustainably, invest a few dollars into a company that aims to create all different things from trees that can be made from it. Like UPM or Stora Enso. They are investing to find new uses of trees to replace the thing that was their main product long time ago, paper.
Your belief that plastic use is somehow harmful is wrong. And your belief that steel is somehow better than plastic is wrong too, actually plastic is better today in the quantities we make it when compared to steel in the quantities we make it.