Can be done for the price of two washers. Doesn't take very long if you're just adding the washers.
When I got my K1100LT the rubber mounted handlebars were kind of mushy. I found this
and decided to give it a try. For the cost and effort it makes a big difference.
I got my K1100RS several years later and after having firmed up my LT bars the RS bars felt like mush so I decided I had to firm those up as well. The bike was a Malibu bike and even though the rest of the bike didn't have signs of corrosion I was somewhat shocked when I pulled the handlebar mounts apart.
The handlebar mounts on the right are the ones that came out of my RS. :o Both the studs of the lower mounts and the metal tubes they go through were pretty nasty. So I replaced them with mounts and lower clamps from a parts bike. (Left side of the picture.)
Those rubber mounts were kind of hard to get out. This is the "BMW special tool" I came up with for extracting them - a long 1/4" ratchet extension and some Vice-Grips.
And here's the stainless washers I used underneath them to help compress the rubber mounts and firm up the steering. I don't know the exact dimensions of those washers but the key is to use washers that have a large enough inside diameter that the studs can pass through and an outside diameter small enough to fit in the hole in the upper fork tree.