Who stocks low or zero level of Formaldehyde chipboard.?

I wish to overlay my existing floorboards with a chipboard product with low or zero levels of Formaldehyde. Screwed down at 6" centres, it would not be spanning floor joists, so not load bearing, just levelling out uneven floorboards. What products would you recommend, and a supplier in the Tyne/Wear area of the of UK., please.