You can get a free companion certificate by getting the Visa card affiliated with United and paying the annual fee for the card (I think its around $65 for the regular card - and if you are elite with United you can get the gold card for the same annual fee).

If you have kids in college enroll them in United mileage plus college program. They will mail you some certificates, one of them is around $200 plus tax from East Coast to COS (you cannot use the cert for Denver, but COS is ok). Post a message to see if someone has that certificate which they could give to you or lend to you.