You can build a DAC from a 5.1 (6 channel) or 7.1 (8 channel) sound device.
You need to know how to solder pretty well.
I sell a kit that you will need. The kit is $40 plus shipping.
Look for the USB SND8. This is a good 8 channel USB sound device.
You need to tack solder 6 wires onto the back of the sound device PC board.
Then you need to build the kit.
Once you build the kit you need to hook up the sound device and test it and tune it so that it will work with an ILDA controlled projector.
A laser projector with an ILDA port is controlled by a set of 5 analog voltages.
X, Y, red, green, blue.
X and Y control the position of the beam and red green and blue control the color.
LaserBoy makes wave files with 6 channels, that contain those control signals.
So you can make your show material in LaserBoy and convert that into a 6 channel wave that, when played through the sound card DAC, will produce the analog voltages necessary to display your show on the laser projector.
The LaserBoy software is free.