So I need to buy some new focal lenses for my 100w Nova 35 I'm told they are 20mm diameter 2" inch focal. Manufacture tells me $60 usd each plus shipping. Online I see lenses with these specs on Amazon and eBay in the $32 Canadian range with like $5-$8 shipping. The ones that came with the machine didn't even last since November so I'm kind of skeptical that they are any better than the cheap ones. Can anyone offer some advice, brands places to buy etc.