Found these models when looking for a way to recreate the vehicle found in this TMP post. I thought the Triarch Stalker would make a good vehicle for a Mad Scientist bent on Domination of the Solar System.
Triarch Stalker (40K) Proxy / Alternative: $50 from here
SM / SoB Whirlwind Alternate: $16 from here.
Necron Scarab Alternate (x12): $10 from here.