I just picked up the Insignia myself and found the plug from the source. I planned on getting the $99 19" but ended up with the 24" for $130 CDN. I found that the Insignia needs a type-M adapter. I believe the 19" is rated at 26W whereas the 24" is 30W. The 24" is also 1080p vs 720p for the 19". I'm really surprised to see that it seems to be cheaper in Canada than the US.
For the other Canadians, I'll provide some links:
Insignia 18.5" tvInsignia 24" tv12v Power cableType-M connector for use with above cable