2035
also, the 20202 blue set has the proper plugs as does the
21355 cream and forest green open platform set, as does the original
red one, and the christmas set and the anniv set.
the yellow ones are common, and if you are patient, you should be able to find not only a 2035-usually about 150 US, but also another yellow trailer, which makes for a tiny little yellow train. These are my favorite colors among the LGB tram offerings, I loved the Cologne version too, but they were short lived.
the simplest solution is to buy a two wire LGB connector as used in the modern lighting sets, since your trolley do have plugs, just the modern version,
and simply put the old marklin style plugs on one end. if you're really cheap or cannot find the marklin plugs, often on fleabay, you could double up the wire and simply stuff it in the holes. not as secure, but if you get it right, or solder on a thicker bit, it does work.
I would think, that , you could, possibly, add metal wheels and pick ups, and have it self contained,quite likely the least intrusive way, or, pull the roof and add a ready made LED light and use a coin battery supply.
or,
add a wired tether to one of your others, obviously tapping into the track, and then off to the trailer, using old style marklin plugs.
one thing I have seen, which I like a lot, is to take a 2035, and remove one platform end with headlamp, and swap it with one platform end of the trailor unit, so that each end of the UNIT has a headlight for point to point operation.
One of my daughters has given me for Father's day an LGB trailer 3500 with lighting.
