Wanstalls used to sell them, not sure if they still do? You pay a premium price for Veridian but they are not bullet proof and there is not much customer support from what I've heard from a few gunnutz who've had them. For some unknown reason Veridian says not to use rechargable cells in their units where as the much cheaper NC Star green lasers have no issues with rechargeable batteries and NC star has a better warranty then Veridian.....just make sure you buy it from someone who will stand behind the warranty such as Canada Ammo or Marstar.
What pistols do you want to mount it on? They are great for dry fire practice exercises and obviously would be good in a low light defensive shooting situation.
The chances of most of us ever being involved in a low light defensive situation against an armed person is extremely low.... but it doesn't mean the laser wouldn't be an advantage.