I bought this. It is a two pack so one on each end of the run. The foil was only needed on the flex hose end, the band straps made them tight to back of the Glowforge.
https://www.amazon.com/Rockler-Dust-Right-Ports-2-Pack/dp/B0025AC6MI/ref=sr_1_6?s=hi&ie=UTF8&qid=1515005988&sr=1-6&keywords=rockler+dust