Can a 1.3W rated SOT23 MOSFET deal with 0.9 W peaks?
Use two in parallel - they will current-share because as a MOSFET heats up its on resistance also rises (unlike bipolar transistors). Also mount them with some decent copper on the PCB.

Below are some relevant facts from the data sheet: -



On the upper graph I've cheekily modified the safe operating area and this basically tells me that for a 1 second pulse the limit is somewhere around 0.9W (which is your limit).

The middle table tells me that the junction of the device will warm up about 100ºC for 1W being dissipated and this reminds about point (3) and the amount of copper around the device that restricts this to only 100ºC.

The lower picture tells me that whatever the duty cycle is, a 1 second pulse might as well be infinitely long - the thermal response will be virtually 100% over a period of 1 second.