Woo lots of responses..
Maybe yeah, a putty might be more practical I suppose.. Good thought
i wouldn't epoxy/glue your light to the wall. you need the ability to remove if it you need to change the bulb and/or remove it to get algae behind it. you could try and epoxy a ring/metal around the actual fixture and then tap/screw a new bolt into your wall to hold it in place
would this fix your problem:
http://www.pentairpool.com/pdfs/QuickNicheRepairKitOM.pdf
Unfortunately I don't think it will as when the pool was resurfaced last with the previous owners they did a really bs job and didn't replaster like you normally would, instead opted to resurface with some kind of fiberglass shell and the way it covers the old niche is ridiculous. You will see in the picture below that the entire niche sort of 'recedes' now behind the surface of the pool wall. With no ring (or maybe just broken) with the screw hole tab and bottom clip.
I know what? We need pictures!!! Can't believe nobody has asked yet
I have put some pictures up here previously of this issue. I did receive a lot of good help and ideas but unfortunately no real easy solution. See them below.
You could try a light wedge. They are fairly inexpensive.
Got a couple. But that doesn't solve the problem at the bottom of the niche to hold the light. But I do plan on using them somehow to "assist" in my unconventional install.
Picture time.
This is how I found it when I bought the house (not long ago)
Close-up of whatever this is pulled up on the deck
It is 8" in diameter and ANY light ring adapter I have found is for 10" Also see how it sits behind the pool wall (the niche)
No clip on bottom. Actually I am noticing now that there is a little sort of lip left from what used to be the clip before it broke off or whatever, sort of like how the tab for screw hole at top has some remnants of a previous tab remaining.
And a close up of the tab at top (what's left) and how the niche sits in recesses in the pool wall.
Again I'm not trying to double post, and I did get some good help before, just the paths I was sent down didn't pan out, not anyones fault, they were good ideas.