I found three possible projectors that could help you. They are all light weight, feature a native WXGA (1280 x 800) for your mac, and cost less than $1000.
First up is the Dell 1609X
($849)projector that features 2500 ANSI lumens and a 1900:1 contrast ratio. This projector weighs only 5 lbs and features two RGB connections for your laptop and another source. In addition, this model also has a 8W speaker system that allows you to play any audio you want.
Next is the Optoma EW628
($999) that features 2700 ANSI lumens and a 2000:1 contrast ratio. This model is a little better and a little lighter, weighing only 4.4 lbs. This model doesn't have the dual RGB connections, but it does come with an HDMI port if you wish to use it at home.
Lastly is the BenQ MP735
($999). This model is the brightest of the bunch with 3000 ANSI lumens and a 2800:1 contrast ratio. This projector is a little heavier than the others, weighing just under 8 lbs, but it is still light enough for traveling.