i dont think the above recommendations are what your looking for except for designs as from what i see of their websites they are suppliers only. as your looking for an off standard door your looking towards a small joinery or depending on size you may be able to buy a std door and either cut it down ( check that the door is solid first as most imports are only veneers) or add on some timber slips( the problem there is that the colour of the added on timber over time will look different)
its because you are looking off standard that the price is more expensive as the joinery has to set up their machines just to make one door.
google local joinery's or golden pages were you live for a list