XR 650 R: rubbber gasket for airbox

Hy guys,
I read few months ago (unfortunately I didn't remember where) that during Baja race or during riding in places where there is a lot of sand (i.e. desert), due to the non-perfect sealing between the air filter and the airbox of the XR 650 R several riders fit the airbox with a special rubber gasket.
This rubber gasket should avoid the sand flow into the airbox and, of course, save the engine.....
Do you know who produce this gasket? Where can I find it? Are there other solutions?
Thanks in advance
Paolo

A few of us desert guys line the edges of the filter with good old fashioned grease...Works like a charm!

Focker wrote:A few of us desert guys line the edges of the filter with good old fashioned grease...Works like a charm!

+1 and if you're the by the book guy no-toil sells toothpaste sized tubes of air filter grease. Kinda gooey and nasty looking but it does the job.

I have a K&N filter on my bike. It basically is a rubber mold of the air box opening where the filter is installed they recommend filter grease around the perimeter of the filter. K&N sells a tube for about $10. and it lasts a long time. I have never had a lick of dirt, dust or fine powder inside the box and air flow is awesome through the filter.