Another magnetic dust boot attachment.  This one lives at TechShop Detroit.  .dxf works well with the following materials and is included at the end of the instructable.

3/4 MDF * 
1/2 MDF *
24" Tight-Seal Strip Brushes McMaster item# 74405T14 for 3" steel backing (other sizes available in the same section)
1/2" Neodymium Magnets (available on amazon or ebay) *
1/4 - 20 hardware 
hot glue

* substitute with what you have around the shop.  Make adjustments to .dxf as necessary.