After a quick search ...these mention poly
http://www.oringslimited.co.uk/products/o-rings/
I use a company cally Polymax so maybe worth a try?
Does it have to be Poly?.......maybe Nitrile or Viton might be better.
Let me know mate as i've just checked and can get some Nitrile shore 70 19x2, EPDM or EPDM 70 ShA Peroxide Cured FDA (is the 19 the ID or the OD?)