One thing I saw recently, but wouldn't recommend, was using a ratchet strap to pull the RAs together, somewhat keeping the arm with the missing bushing from moving...
One option, if you just want something temporary before doing the actual repair, would be to buy a new bushing and make a cut in it so that you can slip it around the radius arm, then use a hose clamp to secure it on the arm...you would be wasting a perfectly good bushing though...
I'm gonna sound really redneck here, but if you don't want to waste a bushing, and just want some padding there, have a sawzall and a used tire, would be cut a 1" or so wide strip from the tread surface of the used tire, roughly 24" long, and wrap that around the arm, using as much as you need to, and then using a hose clamp to keep it from coming off...
Last thing, which is what I did for a while with both of mine, is just drive conservatively...plan on braking much earlier than you usually do, easing on and off the brakes slowly, and doing that won't make your RA move around with enough force to do any damage to the openings. It will also let you completely stay out of the snow. I probably wouldn't have suggested that three months ago, but winter is almost over and it won't be much longer before the snow is gone for you to do the work.
Hope that gave you some answers!
