If my memory serves the Mani2's have 3 main elastomers in the stack and a smaller rebound. I just suddenly had a thought that we may be over thinking this, quad skate cushions are about the right size (diameter), pre drilled for M8 bolts, cheap and easy to get hold of. The only catch is the softest they go is 72a, but for me this would probably be OK and I could assemble a stack to the correct height give or take a few mm as they are supplied in 14mm height.
This is what I was thinking of:
http://www.ebay.co.uk/itm/SUREGRIP-Supe ... 72234eb55b
A stack for the Manitou 1 and 2 should be about £20 delivered as you need 8 a side, plus a rebound.
Carl.