I have put together a couple of my own so far, but I'm still in the testing phase. I used a cheap clearomiser I got on ebay and a mini fish tank air pump from Amazon. A little solder to wire it up, and some hot glue with a piece of tubing and attach the two. Then you need a 3.7 volt power source( You can use a DC to DC buck converter) and a way to make the lights and sound board activate it, like a relay module.
This may sound intimidating, but it's actually pretty easy.
I used a tutorial online to learn how to make it.
https://valkyriestudios.net/making-a-mini-fog-machine/ Just replace the remote receiver unit they use with the output signal from your lights and sound board through the relay.
10 pack of clearomisers is like $15, the fish pumps are 2 for $12, DC-DC buck converters are 5 for $8, and relay modules run around $5.
What I'm finding with mine is that if I let the unit set for a week or so between uses, you need to run the setup for a minute or so to get the smoke working again. I'm not sure if that is normal or because of the cheap e-cig parts I'm using. I think I need to add a "priming" button outside my pack to get things flowing before an event.
everyone suggests the cangar K2 clearomiser, but I haven't found a good source for them yet and they are a lot more expensive.
If you want to try your own, I'd be happy to answer any questions I can.
014 by
banjoben42, on Flickr