Used/unused carpet underlay (10mm) (HX3)

Anyone got/know of someone who's got some spare 10mm thick (if not thicker) underlay at all...? Trying to put carpet down in my main bedroom I'm decorating so I can have my children stay over. I've got half the room done, but fell short approx. 3x3 metres ☹️ (Specific dimensions available). Thanks to the lady in the Calderdale area who already gave me some a few months ago; this did two rooms! If anyone can help me that'd be amazing! Thank you!