Tools and Materials
Plain orange favor bag
Mailing label
Glassine envelope
Mailing-labels template
"Bring your bag to collect some treats" template
Candy
Halloween Luminaries How-To
1. Decorate a plain orange favor bag with a decorative border using stamps and stickers.
2. Slip a piece of paper with the party details inside; use the "bring your bag to collect some treats" template so guests will know to bring their bag to the party. Place the flattened bag into a cellophane envelope.
3. Remove the protective backing and seal the bag.
4. Download the mailing-labels template and print them onto adhesive paper; affix a Halloween mailing label.
5. Stamp the invitations and send them to your invitees.
6. At the end of the party, fill the bag with candy to turn the invitation into a great Halloween party favor.
Tip: These bags can also serve as pretty bases for flower arrangements. Simply insert a small glass vessel filled with fall flowers into your decorated Halloween luminary invitation.
Resources
Everything used to make these clever invitations is from marthastewartcrafts.com.

I too found that problem at first, but on the left side panel on the bottom, click on,"on the show", then click on "halloween is almost here, shop now" picture, it would lead you to straight to the halloween supplies.
Where can this kit be purchased? I've searched the Michael's crafts, but this particular kit is not shown.
I love the idea of themed using silhouettes for invitations. I want to save one each year and put them around my lighted (change light color to be more festive) tray ceiling in my dining room. Guests will see the silhouettes from past years and reminisce fun times past. I need to figure out if I can make the silhouette all one piece or if I will use a see through paper backing.