If you are referring to similar as the pic I have often cleaned them by soaking them in lacquer thinner then repeat with fresh clean l-thinner. I have done the same to clean oil bath air cleaners and doesn't harm the, I thinks it's called horse cloth that is inside. Then just give it ample time for the thinner to evaporate after cleaning before re-installing. But the oil breathers are fairly cheap, maybe just buy a new one?
Those look more like the ones for valve covers, which are different from the crank case ones. I'll take a run to NAPA and see if they have replacements. Mine has a skirt halfway around it which I guess acts as a bit of a splash shield.
No worries. I just took the PCV valve off and cleaned it with some engine degreaser. The valve was floating free, but I want to be thorough. Pulled the cap off the crankcase breather and squirted it with some degreaser as well. Letting it dry out before putting it back on. One thing I noticed is the air breather assembly has a nipple on the bottom of it. I am wondering if that's for hooking in part of the PCV system. The way mine is hooked up is there is a plate under the carb that the PCV valve is attached to, and that leads to the back of the engine via some tubing. THen off course the oil breather cap.