<p>I'm looking to 3D print a structure that won't deform in high heat, up to about 220&nbsp;&deg;C. The filament itself can be 3D printed all the way up to about 380&nbsp;&deg;C. </p>

<p>PEI seems like it could be a viable option. I found some <a href="https://www.matterhackers.com/store/l/3dxtech-thermax-pei-175mm-05kg/sk/MHCFSNUC?rcode=GAT9HR&amp;gclid=CjwKCAjwqZPrBRBnEiwAmNJsNsqaaSEcWYtaTv1rIwDKuWgI9xCyinqDgV7bYUUO3zX7-pIA0gDPSBoCclYQAvD_BwE" rel="nofollow noreferrer">here</a>. This PEI filament  specifies the glass transition temperature at 217&nbsp;&deg;C.</p>

<p>Would this filament work? Are there any other types of materials that would fulfill this engineering requirement?</p>

Your expected operating temperature exceeds the glass transition temperature by 3 °C. This implies that the structure will become weak and can deform under load.
Note that you cannot simply print PEI on a normal machine, it requires a special high temperature capable printer with hot end temperatures up to 400 °C and heated bed over 120 °C up to 160 °C, furthermore it will need a heated chamber (up to about 80 °C) which requires special care to cooling and placement of electronics and motors.
Not having specified what kind of structure you require, you could look into steel.