The Megaforce Bikes are more than likely something off the shelf with relatively minimal modifications compared to the Land Probe since they had to do practical stunts with them (wheelies, jumps, flip over crashes). I would also be curious to see what they used. I don't know if a kit was ever done of the Mega Cycles, but one of the Japanese firms did the Mega Cruiser in kit form in about 1/24 scale. I've only ever seen ONE of those in person.
BTW, the Land Probe turned out GREAT! That is one of my three favorite bikes from that era (the other two being the MegaForce cycle and Streethawk, of which one of the stunt bikes is now owned by one of the original stunt riders from the show).