I used to work for a company called 'Flexiski', they specialised in such things as short stays etc and they are in nice resorts too......trouble is they ain't cheap.
I'm assuming there are other companies that do similar so i'm afraid it's a case of internet searching.
That said...if you want it cheap and not for your normal 7 day holiday stint, you may be better getting on tinterweb and booking accommodation separate and then sorting flights etc to suit......or drive?
Not massive help I know, but most resorts will have accommodation that is flexible and bookable last minute...it's just cheap flights and transfers you'd need to factor in too.