I am looking for sources of materials to seal my crawlspace. 


First I need something heavier and more durable than 6mil poly.  Also need a good adhesive to attach to concrete block and tape for the seams. 

Second, I have a sump pump in the crawlspace, do I need to worry about a perfect seal or is there a different lid available?

Thanks

Forget taping the seams- use duct-mastic both as a sealing adhesive to the concretes blocks and sheet seams, overlapped by at least 8", and the exposed edges of the overlap. A paintbrush or flexible plastic putty knife works fine- metal is more likely to cut or punch holes in the poly. In addition to the mastic, mechanically secure the edges of the poly to the concrete block with furring strips. Taking the sheeting up to within 2" of the top of the foundation is better than trying to vapor-seal the block with goop. A small gap at the top is useful (in some places mandatory) for termite-inspection.

The seal at the sump doesn't need to be anything like perfect- it's a tiny fraction of the total area.

6 mil poly is pretty durable unless you expose it to UV or plan to walk on it. But if you're feeling rich a 2" rat-slab poured on top of it will protect it forever. Otherwise some planking where you need to walk to service the sump, etc. never hurts.

Use InSoFast on your crawlspace walls and it will be vapor barrier and insulate it.