I have seen a window cleaning suppliers sell a 27 litre one for just over £9.
but if you go to a cake makers (to be specific) , they will sell them maybe give them to you.
however they are smaller (about 10litre) but the still do the trick.
for me I only paid 50p for each tub I wanted. the pasteurized egg ones are best the seal on the jam ones isn't to good but I use that for WFP spare parts.