Filtering fuel before filling the tank

Would be too restrictive for filling a tank from servo pump

you can get special funnels from diesel suppliers etc, that have a micro screen in them that even stops water going through. Ok for jerries / hand pumps, but no good for bowser.

Cant think of anything that has a low enough restriction and a high enough flow rate to suit electric bowsers.

I know this doesnt really answer your question but a toilet roll bypass filter can be fitted , have does this to my engine oil and intend fitting one to my diesel supply , only problem is space to fit it , sounds ridiculous for a Tojo Cruiser doesnt it , but turbo gear does take up a bit of space . Try Googling Franz Filters and there are other makes

I did look into this myself after a few tanks of dirty fuel on trips.
Closest I could get was a type of sock placed in the filler, but it also results in a slow fill.

Ended up putting a 2nd filter in the fuel line just after the tank, with it's own pump.
I checked with the mob who overhauled my fuel injection pump and they said any excess fuel at the fuel injection pump on the 2.8l pajero just gets returned to the tank anyway.

The pump does 60l/hour, so the whole tank (135l) is turned over in about 3 hours of running. If after a few hours of running I notice a slight drop off in performance due to a blocked filter, I just clean it. Nice and easy to get to up on the side of the chassis near the tank. Thought I had a dirty filter on Saturday, took me 5 mins to take it off, look and reassemble. Just run the pump for a few minutes to reprime.

Main filter is still a 11 micron filter (left it in as a fail safe), while my 2nd filter is 13 micron. Not sure if a sock filter would go that fine. Main filter is $30.00 to replace, 2nd filter is $10.00 :-).

Us yachties use a thing called a "Baja Filter" which is an American invention and used by yachts going to Baja California/Mexico or any country where fuel quality is a problem. Most yachts travelling internationally use them. It consists of a aluminium tube/funnel with 3 fine stainless steel mesh filters which slide in (and out for cleaning. They pick up everything including water. As already mentioned , any filter slows down filling the tank. Landrovers years ago (maybe still do?) had a tube with a mesh bottom which fitted into the filler tube which could be removed for cleaning.

Bja filters can be purchased from some yacht chandlery shops but you could Google "West Marine" in the US where I purchased my one from (few hundred dollars)

If I was driving through a third world type of country, I would definitely use one.