I'm short of meltaguns myself so afraid I can't help you on that one (I only have 1).
although I do have a few odds and sods that I could do some sort of swap for if people want them:
IG - I have an old Yarrick and a slightly battered chimera
Eldar - I have a maugim'ra death reaper guy who I believe is an HQ of somesort, seems to be OOP from what I can tell
GK - Eversor assassin and other "normal" assissin with sniper rifle
that's all I can recall of the random models off the top of my head, think I have a couple more SM bits a chaplin or something....
Oh and loads of nid bits, that I'm really forgetful at bringing with me when people ask.... :-D
Anyways happy to look if people want stuff!