Since sending two emails from the contact us link for PIAA and receiving no response over two days I called 'em yesterday and they said to use Gorilla Glue to affix the lens to the body of these lights. I've used Gorilla Glue before and am dubious about its sealing properties. Any other reccomendations would be welcome.
I just got another email from PIAA "That is an old school P-1000 lamp. We no longer have any bulbs for that lamp. You can try and search the web for some part number is 13355. As far as a specific sealant I would go with and epoxy it will have better strength than an RTV".
So it looks like I need to find a high endurance epoxy now, if I choose inkeeping with PIAA's reccomendation.