Keep dirt out of throttle tube with zeta HG installed

So I installed Zeta hand guards which required me to cut the end off the throttle tube and grip. Last weekend I dropped the bike over in some very fine sand and some got between the throttle tube and bars and was causing the throttle to stick. Was able to work most of it out to keep riding, but the throttle still doesn't snap back as briskly as it had before so I am going to have to pull everything apart to clean it. Any tips for installing bark busters AND keeping dirt from getting between the throttle tube and bars?

I thought about instead of cutting off the whole end of the throttle tube, cutting a hole in the end of the throttle tube just big enough to insert the HG but still leave enough overhang of the throttle tube to cover the bars. However, this would require me to have the HG insert pulled out a mm or two for clearance. My fear is that if I go down, it could push the HG into the bar end and jam the throttle tube against the bar end.

My zetas came with a little plastic washer for the throttle side...may have helped keep dirt from jamming in there. My lil washer is now, worn right out.
I've dropped it many times with the washer on...never, since I took what was left of it off...never had dirty throttle issues...so, who knows?

Yeah, I have that clear little plastic washer as well. And I have dropped it on that side before, but it was when I fell in sand that I had the problems. My little plastic washer is a little bent up. I wonder if you can buy replacement ones or if there is something I can get at Lowes or Home Depot that would substitute.

Make one out of a plastic jug...