swingarm rubber plugs

On the inside of the swingarm, on eitherside of the rear shock, there are two openings shaped like 'D's in the swingarm. The fiche shows no plug for this hole, but other pro-arms do have a rubber plug. When I took out the eccentric carrier, I found a beer cap, a battery bolt, and about a half poud of road grit, helping to jam the eccentric carrier from the inside.
Has anyone made plugs for these holes, or found other solutions? I plan on getting rubber plugs made for the pro-arms from other models, hoping they would be the same size.

 

I stumbled upon this same problem with my 1997 VFR. Here is how I solved it.

http://www.ryanchapin.com/vehicles-and-machines/1997-honda-vfr750f.html