I use the 8kg cat carrier from Pets At Home. Those four are only 1.5kg each, so they are within the weight limit.
http://www.petsathome.com/shop/large-wire-door-carrier-for-cats-and-small-dogs-by-roadrunner-13618
That's it. They do two sizes- 5kg and 8kg. I have both, but use the 8kg for threes and fours of my nethies.
My four have this one...
http://www.petplanet.co.uk/product.asp?dept_id=327&pf_id=52107
It's super. I have three 1.8kg bunnies and one 1.3kg. The top is really REALLY useful. In the car on the way I open one side and can stroke them and settle them.
ETA: I do have to take the food tray out though for space but I don't use it anyway.
My four have this one...
http://www.petplanet.co.uk/product.asp?dept_id=327&pf_id=52107
It's super. I have three 1.8kg bunnies and one 1.3kg. The top is really REALLY useful. In the car on the way I open one side and can stroke them and settle them.
ETA: I do have to take the food tray out though for space but I don't use it anyway.