To make one, paint a drop solid black, punch holes in any manner you'd like. Hang a mylar slit drop upstage of it and light the mylar from above, below, and from the sides (all sources generally ds of the mylar drop). A fan or two on the mylar will add some twinkle. Different
colored mylar, or different colored light on the mylar will add, well, color.
Christmas tree lights hung from a batten, spaced an average of 9" apart, against a black background with a black scrim in front, look very good. My crew covered the majority of those little lamps with scraps of blackwrap. It did take the crew several hours to randomly mask the
lamps... The result was very effective and very cheap--I think I spent about $120 on the 19' strings.
Just buy a couple of rolls of black photo backdrop paper to use... (an even cheaper solution would be to use black, 10 mil visquine sheeting, taped together using black gaffers tape) Lay them out on stage, glue the seams together into a cyc, and attach the whole thing to a batten. Then, as you slowly raise the thing (about four or five feet at a time) you and some assistants can punch random holes into the backdrop using nails, knitting needles, awls, whatever will make a neat round hole. (If you want some stars to be of a different color, you can tape some lighting gel materials over the holes.) After that, it's just a matter of lowering your sky drop behind it, and adjusting your cyc lights to the intensity you want.
Another alternative is to buy several dozen of those Christmas light decoration "nets" (The kind home owners use to cover shrubs and bushes with.) and attach them to a batten in front of a black curtain. This will give you a much sharper, intense star field than anything you
could achieve using reflected lights. You could also plug these nets into your light dimmers so that you could control their intensity somewhat. Keep your primary stage lights off the background, and the audience will be unable to see the wires because of the lights
themselves. Rather like being able to see the headlights, but not the car.
When working on a Christmas revue several years ago, I used the punched hole star field for the background stars, and used a single, 12v halogen hanging in front of it for the "Star in he East." The audience reaction to a single Xmas tree bulb being ramped up on cue, (gasp,
awe) was very gratifying.
I closed the mid-stage traveller to within four feet, and tried the "poked hole" technique using an old muslin flat. This technique lets you control the placement, and the intensity quite well.
The drawback with it will be the expense.
Next I tried putting a few of those cheap Christmas strings onto a batten. This looked fine, but a little too regular. There would have to be a lot of custom tinting and removal of bulbs to make this approach look like a natural, random star field... Also, even though the lights I used were of the "clear" variety, they had a definite yellow cast to them, being unfiltered incandescent bulbs.
Next, on a whim, I tried grabbing a box of sequins and pins from the costume shop, and began poking them into the black traveler. In about 15 minutes, I had a 12 x 12 foot area decked out. The stars were about five or six per square foot. Turning on a fresnel, aimed directly down onto the traveler, I found I was staring at a very impressive star field. The drawbacks of this are the labor intensity, and the fact that you'll have several hundred straight pins sticking into your cyc.
There are "tagging" guns used in retail to put those tags on clothes. They push nylon "T" shaped thread through the fabric. The same thing is available for quick button attachments. (Button Mate?) I think you could find them in the fabric stores or in the fabric department of some larger discount stores.