I wanted to get a fancy ring light for my DSLR, but all the ones I could find were not built for my lens (18-135 STM) and they were too expensive - and so I've had to make my own! :)
First I ordered some LED ring lights that are *meant* to be used in a car interier, they are 12V DC and in my mind - ready to go for my project!
I got the ones that I needed from here (search for the sizes you need)
Then I orderd a LED dimmer, the dimmer is supposed to be used with the LED strips but it worked perfect with the rings too - I go mine from eBay - Like this one
and finally I designed and printed the holder that will fit the rings and also fit on my lens' hood ring part - I have provided the STL file in my Downloads section - if you have a 18-135 lens then it will work for you :)
Here's some pictures and a video of the light dimmer working - in the pictures there are some with the light ring, and some with the flash, and some with no flash - the best one's (to me) are the one's with the ring light :)
Check out the video on my YouTube Channel (I embedded the video here but Flash's "I got to be on top" was messing with my pictures! LOL