I don't have anything like that in my "spare" parts collection. Four possibilities:
1. Leeann recently posted the name (and maybe link) of a warehouse full of parts like that stripped off old motorhomes.
2. Some of the online RV specialty stores have new replacements for some fixtures like that. (Google "RV parts" or "RV lights" ... or check eBay in similar categories.)
3. Replace it with a similar LED fixture. (This is my personal preference.)
4. Make a new lens but this requires a bit of practice/skill. (The right plastic, low heat, a custom mold, and -- ideally -- vacuum forming equipment.)
