You want to register a co-domain that is already registered. You can place a backorder for a registered co-domain at ICANN accredited Registrar Secura. You pay 119 US-Dollar. If your co-domain should be registered by a third party, you can use the 119 US-Dollar as a deposit for your next order, or the sum will be refunded.
The .com domain is the gold standard for US-Americans. Google lists at the first page of the US-Version of Google at the most searches websites at .com.
If your name is taken at .com, .co is a good option. The fitting name at .co promises more success than a wrong, but available name at .com.
By the way: If you are not a citizen of the USA, we recommend registering your name at your country code domain extension. Google lists at the different country versions of Google at the most searches websites with the country code extension at the first page.
And if you are citizen of Colombia, you should register therefore your name at .co, not at .com.
By the way: Nobody forbids you to own two websites with different domains.
You could register the perfect name at .co and the less perfect at .com.
If you want to get expired co-domains by us, then please write to email@example.com