Price Paid: £120
Not sure how you managed to block it, mate? I am on my second replacement filter after two years and 67,000 miles on our bikes. It's gone through Columbian infested ditch water while hiding from less than happy chaps with guns and an eye for my BMW, to Australian muddy puddle mop ups in the outback and has almost certainly spared me from perishing on a number of occasions.
There are other systems on the market but I bought mine on a personal recommendation from a squaddie friend who was given his on operations in Afghan. Good enough for him, good enough for my ROW trip, and it's never let me down.
It's never "blocked" either, interested to hear what you put in it so I can avoid doing the same! If it gets full of mud just take it apart and give it a rinse out in a river/puddle etc.