Sorry for the delays in a response!

I couldn't find a drawing or dimensions.

http://www.rollingblockparts.com/no-2.html

Did find that, they have parts. Perhaps you could ask for a drawing if you're dead set on making one yourself. If you're happy to buy, well, there you go!

Edit: Doesnt appear they sell an extractor. Perhaps still worth shooting an email to them.

Cheers,
Ash.