Thanks for the replies so far.

The important thing to note is that the weapons will be made from plastic so if anything does come flying off it is only going to be shards of 3mm acrylic.

These are the things I was looking at:

http://www.ebay.co.uk/itm/142212928164

http://www.ebay.co.uk/itm/252691100748

http://www.ebay.co.uk/itm/201840681700?var=501867119105

http://www.ebay.co.uk/itm/331367359349

You are right actually - I have not paid much attention to the weight because for the purpose of what we are doing it doesn't need to fit a specific category. I guess 1.5kg sounds about right. Possibly lighter.

I had figured that a shard of 3mm acrylic could not penetrate a piece of 3mm polycarbonate but I may be wrong here. The bus company idea is great by the way.