The easiest is made by using a 50ml catheter syringe.
Cut the body to about 1/2, ie cut off at about the 25-30 ml point.
Trim the cath tip just a bit to create a wider opening that will still
fit in the intake hose. Load the syringe body with some poly fluff
to strain the floaties.
Using my current Sawyer Black inline filter I unscrew the
body and put a bit of poly fluff in the input side of the filter,
it has plenty of room.
My next option will be to find a serviceable inline gas filter, if I can find one that is small and light weight and use the body of it as a fluff holder.
Next and what I would consider if you worry about chemical contamination
would be to use a normal inline serviceable carbon cartridge, I believe
Katadyn makes one, just checked, they do. I see that Platypus also makes an inline carbon element but it seems to be sealed, I would pass on that one due to limited capacity and no ability to service.
I also see that Sawyer makes a male and female cap ends, if they will screw
together that could also be a basis for a prefilter or even a carbon element
or both together.