18Sound XR1064. They're meant to be used as 60deg horizontal and 40deg vertical but you could always turn them round!
Only problem is that you have to order them specially from Italy through Noise Control Audio. I will be putting an order in to them for stock at some point but I'm not sure how soon. If there is interest in getting 18Sound drivers I could get one moving. More you buy in one go, the lower the shipping costs.