There were a couple of .25 autos made under the Colt name- one made in Spain until 1969, other made in US 1970-1975. So you have a gun made for a short period of time, at least 36 years ago. Yeah, will be hard to find. Not impossible, just hard-and expensive. While a Lorcin .25 is about $50-$100, a Colt will run about $300.
Will refrain from telling you what a bad idea a .25ACP is. ASSUMING that you are in the US, you can search on-line gun auctions, such as gunbroker.com, auctionarms.com, or gunsamerica.com. If you find one, in addition to purchase price, you will pay shipping to YOUR dealer (where you will need to do purchase paperwork, background check, etc) and pay your dealer his fee for his time to do that paperwork.