what lens do I need?

I'm new to all this, so my apologies up front.

I'm looking to get a spotlight about 2-2.5 inches (~5cm) in diameter from about 12 inches (~30cm) away with no spill. Ideally, the front will be flat, not rounded. Where would I look for something like this? I literally have no experience.

I'm actually taking apart a sipik flashlight. The focus lens is decent on this to approximately what I need, but there's a tad too much spill and the lens is rounded in the front. I'm trying to modify this to make a temporary dental loupe light for a friend. Her battery on her $300-$400 light died and it costs $125 or so to replace. Seemed kinda ridiculous.

If I'm totally off base with what I'm trying to do, please let me know.

do you want the light to be about 50mm or the spot of the light at 30cm?
A fresnel lens could be perfect for this as it is flat and lightweight. If defocussed a bit, it will give a nice round and even ellumination size depends on how far you focus it.

I'm not sure what light you are taking apart, but if it already uses a lens to focus the light and you're getting too much spill, chanses are that this is caused by an edge around the lens (to mount the lens somehow) or by light reflected off the walls around the LED and between the LED and the lens.

Perhaps you can have a look at the link in my footer to get an idea of what you can do with fresnel lenses.

regards,
Johan

I'm right now looking at a TIR optic on an XRE doing exactly that, although it was custom-modded. Are you wanting to go and buy a light, or might you make it yourself? If you go for DIY, then you could do this easily with about £10-15 ($15-20) of parts.

A lens is quite inefficient, whereas a TIR is very efficient, so you'd get more light for a given LED. Also, what emitter is it, and how many lumens?

Wow. Great suggestions from both of you. I'm looking for a uniform, tight beam of light with no hotspots or spills. As a dental light, it has to shine into the mouth, but not into the patient's eyes.

The fresnel lens is a clever idea and would definitely reduce the weight. Even at 25mm, the diameter is still probably too big for a practical loupe light. The ideal diameter is closer to 15mm. Not sure that's even practical.

Where can one buy TIR lenses? I can't find many sources.

The light I was hoping to sacrifice was a knock-off sipik sk68:
https://www.google.com/search?q=sipik+sk68&oq=sipik
They cost less than $4 and I already have 3 of them. Cheaper than ordering the parts separately as well. They all have Cree lights, but I can't tell which ones are in each (they differ from each other).

At this point, I'm considering buying a AAA light that has a small, detachable head. But I can't tell which ones have the narrowest and most even beams.

I think I have 2 20mm frensel lenses lying around somewhere...