By Mai Martinez

(CBS) – A Chicago woman is on a mission to find the perfect dress for a July wedding, but it’s not what you might think.

As CBS 2’s Mai Martinez reports, she’s looking for a particular dress – one with a deep, personal connection to a sister she lost.

Chicago Police Officer Terry Almanza was a picture-perfect bride on her wedding day, surrounded by her sisters, including Alicia, who wore a purple dress.

Alicia had been battling Adenoid Cystic Carcinoma (ACC), a rare form of cancer with no cure, for about 17 years. She refused to give up, but on Christmas Day 2013, Alicia lost her 22-year battle with the disease.

A few months later, there was cause for celebration: the engagement of Alicia’s only child, Courtney.

Which brings us back to that purple dress. Terry wants to wear it to Courtney’s July wedding, as a special way to include her late sister.

“I know that she will be there in spirit, but I just felt like any extra touches that we can add to that day,” she says.

The problem is, the dress was sold a few years ago at a garage sale. Terry has shared her story on social media, hoping somehow the person who has the dress will hear about it.

Alicia and her daughter started Attack ACC,  a foundation that raises money for ACC research.  So far, it’s raised more than $250,000.

Terry says even if she doesn’t get the dress back, she’s glad her mission to find it has people talking about the deadly disease.