Rusty Wood is the only one in Canada that comes to mind that may know how to do a "Drop Two" conversion on an 87 (he's a member here).Other than that the best I can sugest is do it yourself or try Capt. Coyote in the States, he pioneered the concept.
I have an 87 that I made changes to that seems to work ok if you want to try it yourself. It isn't only a "drop in and use " sort of thing, it requires some modification to the gun and a new home built part. They are all internal mods so are SASS legal.
First thing is to get a new mag follower built. Use steel (I tried Aluminum first but it is too soft) that is milder than the steel that the elevator is made of. The elevator in mine was hardened so any hot rolled will work. Build the follower the same as the original exept for the front end that pushes on the shell. In the front you will be cutting an indentation to acomodate the two tips on the end of the elevator. this indent should be cut about 1/8" deep and about 1/4" in diameter out from center to begin with or so that the tips of the elevaror just enter the cut. Final fitting will be done later. The tips on the end of the elevator need to be radiused with a dremmel on the bottom a little bit to fit the cut in the front of the follower (just more or less take the sharp edge off so it doesn't chew up the new follower with use).
Now you will notice a flat spot on the frame between the mag tube and the chamber. You will have to use a Dremmel to turn that flat spot into a V that will direct the bottom shell into the mag and the top shell into the chamber without hanging up. Be carefull not to remove any more material on the chamber side than is absolutly nessesary.
Now for the fitting of the elevator and follower. With the gun assembled and the tips in the indentation on the follower,drop 1 dummy shell (use an exact size dummy, not one that is shorter or smaller in dia.) into the gun. If the top of the shell is higher than the V that directs it into the mag, dissasemble again and cut the indentation dia. a little larger. A tip here is to cut the indent with a small bevel so that when the gun is closed, the elevaor will pop the follower back into the mag tube without chewing it up. This allowes the elevator to return to rest position if no shells are in the gun. You may have to do this fitting process 2 or 3 times to get it right. It must be set so that the bottom shell is directed down and the top shell goes up when pushed into the V by the bolt.
Once you have the proper elevation set for the bottom shell you should be good to go with 2 shells. You will notice that with the proper amount of pressure while putting 2 shells in that the tips will catch in the indentation, stopping the elevator from going all the way down to the rest position, directing the shells into thier proper pipes when the lever is closed. If you push the shells in too deep they will push the elevator down too far. This can't be overcome as the elevator has to be able to go past the follower detent at some piont for the gun to work properly.
Realy very simple to do if you have a small lathe or a machinist friend.
Good luck