What size lens should I get for my projector?

I found the following video:

And I want to make a $100 1280x800 projector. In the comment section in that video he says he used a 120mm fresnel lens for the back (Focusing the 100W LED to the 5.6" LCD) and a 220mm fresnel lens for the front (Focusing the LCD to the wall). I want to make sure that I get the right lens. 

Here is the site I am probably going to buy from:

I might even post an article that links to their site so I can get the lens for free.

Lastly, I'd like to say that I want it to as small as possible (Hence the reason for getting a not-so-common 5.6" LCD instead of a common 7"). Please help me choose a lens that will allow for the smallest possible space between the LCD, lenses, and light. I will make an Instructable for this later on. 

iceng2 years ago

Your link to BHLens showed $3000 lens cost ?!??

Are they joking ?

knexpert1700 (author)  iceng2 years ago

That says $3

Got it "Price: $3.000" is $3.oo

They are an international company .... explains the third digit.

knexpert1700 (author) 2 years ago

Nevermind: I found a guide for choosing a lens and found that BHPA120-2 fits very nicely with this 5.6" display.