Make your own decoder and encoder using PIC's, which is basically what the Holtek devices are (although they may be different micro-controllers and not PIC's).
One very aggravating thing about holtek encoders and decoders, well the ones I used anyway- HT12A and HT12D is that they require the transmitter to always be on.
I forget exactly how I did it, but I rigged the encoder up so that it doesn't send out a constant signal, it only sends out a signal when it is triggered.
I see one reason pic's eat lesser power and even lesser when in power down mode in compare to 89c2051,89s52 etc.
and i think at same cost and ease of availability
low power atmel chips are harder to find