The system your a member of will dictate the materials form which your weapons are made of.  LARP systems such as Fools and Heroes and Shards use Latex weapons (see Larp for these), whereas systems such as the Medievil Society use ‘real’ weapons (see Re-enactment for these).  These pages contain links to Larp and Re-enactment weapon suppliers in the UK, USA and other countries.  The Wares link will take you to suppliers of weapons harness, tankards, plates, materials, and other such odds and ends.