I have taken my DIY primaloft UQ down to 26 degrees and been fine. it's made of a sheet of 3oz per yard and a sheet of 4 oz per yard if i remember correctly. You could easily make one with a single sheet of 6oz per yard primaloft for relatively cheap. Last i checked http://therainshed.com/
had the best price on primaloft. could be a fun project. i don't know of any manufacturers that make them though. if you can't make one yourself you might look into having someone here custom make one for you. just a thought.