craftgrrl | Molding and casting help.

I need to make a cast of a semi-large object--I need to end up with half a leather combat boot made out of something that's not leather. I have a VERY limited knowledge of casting and mold making--I know making the mold will be the biggest challenge.

Does anyone have any resources for mold-making that won't kill the bank or my sanity?

I was thinking of casting in latex, as this has to hang on a canvas or a board and plaster would be too heavy, I think. Does that sound right?