hazel / cob "Halls Giant": which variety to cross-pollinate it?

[nmayhew]

hi,

i was given a young cob tree "Halls Giant" at christmas, but now find that it should really be "with" a tree of a different variety to cross-pollinate etc

does anyone know which varieties would work, and where i could get them now (the end of the tree buying / planting season as i can see)

many thanks,

nick

[Two_Sheds]

wild hazel - see if you have some nearby