How do I find a 120v charger for my Thor 2.5 million candlelamp spotlight?

Asuming it is the right connection, you have to check the polarity and a page is correct, then yes

If the voltage and tip polarity of your replacement charger matches the charging port on your spotlight, there's no reason why it shouldn't work as a substitute for your original charger. Note, however, that if your original charger was more powerful (say, 1.5 amps instead of the 1-amp charger you have here), it will take noticeably longer to fully charge your spotlight than the original charger took. it's not a problem if the original charger had a lower mA rating than the replacement in your hand--the spotlight will sip an appropriate amount of juice from the charger.

You should be able to use any AC adaptor that puts out a 12 volt DC current and has correct polarity. Based on the estimated size of the battery powering your spotlight, you probably will want a charger that provides at least 1000 mA of power--the charger that came with my ThorX 10 million cp spotlight puts out 1500 mA to charge the two batteries in that light. A lower amperage rating will increase the amount of time it takes to charge your light, but it should still work.
You can find a replacement charger at Radio Shack, which sells chargers that can be fitted with a variety of different tips. However, you might be able to find a cheaper universal charger with a tip that works at a discount store like a Walmart, or you might get lucky at a thrift shop or second-hand store and find a 12v charger that will work with your light. 12 volts is a common output for a lot of different devices, so it shouldn't be hard to track a replacement down. Just make sure you have the adaptor tip polarity correct, or else you could make your battery explode if you try to charge it with reversed poles.

My Thor X 10 million candlepower spotlight takes a standard 12 volt, 1500 mA, center positive AC adaptor. You should be able to find one with an appropriate tip at any Radio Shack store, but you may find a cheaper universal adaptor at a Walmart or even at a "Dollar Plus" kind of store. An adaptor with a lower mA rating will take longer to charge your light, but it should still work (down to about 750-800 mA, I'm guessing).

Double-check the charging port of your Thor light to see whether there's any information about the input voltage requirements. On mine, the light itself has the charging port labeled for 12v, though I was reading the more detailed specifications off the adaptor itself. I can't recall whether the 2.5 million candlepower light also uses 12 volts of power (I think it does), or whether it takes 6 volts (a single battery vs. two batteries wired in series).

It uses a Class 2 Transformer to charge the battery. The input is 120V AC 60Hz 9W. Output is 12VDC 300Ma.

Most of the Vector spotlights use a class 2 charger with an output of 12VDC 400ma with a positive (+) center connector, which are very common. I have several of these chargers from different manufacturers, and I use them interchangably on whichever spotlight I happen to plug them into.
One complication with my Vectors is they use a coaxial connector plug on the spotlight end that is a size N, which is being phased out and Radio Shack doesn'd even carry any more. If you hae a box of misc chargers, find a 12VDC one with a connector that fits your 1.5MCP light, and that is probably the one that came with your light.
Note that you can also charge your light with the cigarette lighter adapter cord that came with it. So if you can't find an AC transformer that fits but you have your cigarette lighter adapter cord, you can buy one of those cigarette lighter size gadgets that plugs into an AC outlet, and then plug your cigarette lighter cord into that.

INPUT: 120VAC 60Hz 18W
OUTPUT 12VDC 1A.

This is the spec for the 18 million thor cyclops which i presume will be the same for the 15 million.
Red light on torch flashes while charging. As soon as full charge is done red light stays lit.

You can purchase one from Black and Decker, they purchased Vector in 2006, here is the link;
http://www.dewaltservicenet.com/servicenet_home.aspx?AspxAutoDetectCookieSupport=1