have you though about making one? check out youtube, they all seem really simple to make and not very time consuming. buying a reptile incubator can be very expensive, if it is only used once a year its gonna take a while to get your moneys worth. just a though mickey
If you've got an tropical fish shop near you, go ask them for a poly box. Most fish shops will give them away but just tell them that you're using it for transporting fish.
Or an old fridge/freezer. I've got one that's gonna be getting converted shortly.