For those looking for closed cell weather stripping for hatch lip building I have found Ace to be a good place. Guess that is why they say "ACE is the place". They have their own brand and it is the only brand I have been able to locate that has 1/8" thick and 1/4" thick. These two sizes seem to work good together, for building the lip use 1/8" and for final seal the 1/4".
I built my hatch lips with 1/8" and had a hard time finding 1/4" anywhere, HD, LOWES, True Value, neighbors back door...
Hope this helps. Joe