Air filter - what to do?

When I was changing the tank on the R1 last week, I thought I'd have a look inside the lovely fabricated airbox and imagine my surprise when I discovered that there was no air filter and one of the throttle cables is held in place with a zip tie
Refer exhibits 1 thru 4 below:
The throttle cable will be easy enough, just remove the zip tie and use a nut as per the top throttle cable, but that necessitate removing the throttle cable to to slide the nut on
In regards to an air filter, I imagine I would need one just to keep dust etc out of the carbys and possible modify one to fit over the front of the airbox, but which one to use?
Would be easier to put a filter on each of the carby trumpets?
Any thoughts......

Refer exhibits 1 thru 4 below:
The throttle cable will be easy enough, just remove the zip tie and use a nut as per the top throttle cable, but that necessitate removing the throttle cable to to slide the nut on

In regards to an air filter, I imagine I would need one just to keep dust etc out of the carbys and possible modify one to fit over the front of the airbox, but which one to use?
Would be easier to put a filter on each of the carby trumpets?
Any thoughts......