Swallow aquatics? Any near you? That's where I got mine, apparently they get them in regularly. (That's East Harling branch though, not sure about the others)
You could always get someone to order you some in.
realised I'd missed the obvious with this. My angels have spawned several time but the eggs have only ever lasted a few hours. Think I'll be moving a pair into the 3ft shed tank and have a crack at breeding them instead.