I found that page... but as with all things Strand... finding answers is a pain... but your comment about it not being a metal part sent me back because the part I saw was metal... Turns out that it was a colortan 1k fresnel that I was looking at and not a Strand... However, it is the clips I see being used on the colortan... the problem is that they aren't needed for a Strand or Colortan fresnel... They are actually for an old Century 3342 fresnel but the system is the same. The lens fits into the housing and are kept in place by three spring steel clips that slide over posts....
I've seen these things being used for something like car fittings, but for the life of me can't remember where or what they were used for. I suppose I could drill a hole and make a retainer... I'd rather find a part to do the job.
Best thing maybe would be to post a picture of the clips...