Depending on how many toggles you need to cross over, I was going to suggest getting a hunk of 50 pair phone cable - although that appears to be way overkill in number of wires needed. Plus there is the issue of there being just 25 wire colors - so in 50 pair, there are two of everything, which gives you a 50-50 chance og hooking up the correct green pair the first time - in reality, since this is Murphy's favorite hobby as well, there's pretty much a 0 chance of getting the correct one.
However - instead, you might want to get (usually fairly cheap since it's not used much any more) Cat 3 network cable. 4 pairs per cable, so obviously you will need more than one cable to connect the two panels. But - take each cable, and then bundle the individual cables into one bundle crossing under the middle of the layout to the opposite side and you'll have a fairly neat wiring system. The telephone/network wire is heavy enough for Tortoises and LEDs, no need to go with thicker wire for that. And with 4 pair per cable, you cna combine a couple of toggles into one cable, reducing the number of individual wires crossing the layout.
There are places online that sell 25 pair cable as well, by the foot. Worst case i can see is you might need 20 feet, which works out to a whopping $25, plus shipping. But that's just the first place I found, not sure if they ship to Canada. If 25 pairs is enough. The 50 pair is slightly under double the price.
Edit: Looks like there are 29 total LEDs and toggles on the smaller panel, so a 25 pair plus a single 4 pair cable would do it. Depending on how you are hooking up the LEDs, maybe some will have a common connection, using 3 wires per 2 LEDs, instead of 4, in which case the 25 pair would be just about perfect. Once single cable stretching from panel to panel under the layout, neatness defined. Under the face of the panel might be a different story 
--Randy
Modeling the Reading Railroad in the 1950's
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