For the lens requirement: “flat fresnel lens for stage light with size 130mm and focus 50mm” from victor_jiake on DHGate. http://www.dhgate.com/wholesale/search.do?act=search&sus=&searchkey=flat+fresnel+lens+for+stage+light+with+size+130mm+and+focus+50mm&catalog=#Homesearch201403 This has increased in price since I bought mine, but it works very well. Perhaps you had a single element lens in mind, but this more than fills the requirement and has advantages of compact size and light weight. Here is my testing thread Fresnel lens tests
I’m in for posting anyway.