I bought something like this from ebay:
The body fitted perfectly and the neck area is wide enough to make internal adjustments like Sten suggested. The padding is usually polystyrene so you could use a hot iron to mould it to size or what I did was slit the cloth and remove surplus polystyrene with a sharp knife. These cases are not hiscox quality but are adequate for domestic use. If you are a gigging pro I would go for a hiscox.