I think the bill added up to around $15. It's a Harbor Freight 12" by 9" tool bag mounted to one of their plastic cutting boards like for in a kitchen. For around $7, you get two cutting boards made out of white plastic, about a quarter of an inch thick. Using the smaller of the two, I cut off the handle on a bandsaw, but a hacksaw would be just fine. The idea is you're making a platform, exactly the same size as the tool bag. Now, using the worthless little rubber pad between the seat and the tail light as a template, mark the three holes on the cutting board and drill them out with a 1/4" drill. Now you can mount the cutting board right on top of the rubber pad. Not bad. A little bendy, but probably no big deal. Now you have a platform on the back of the bike. Grab that tool bag and hold it up on the platform and drill 4 holes right through the bottom of the bag and through the platform. Choose your drill size appropriately for the screws or pop rivets you will be using. I chose some 3/16", wide flange pop rivets and used wide flat washers appropriate to the 3/16" pop rivets. Doing this spreads the strains out over more of the bag material to lessen the chance of a tear. I put one rivet in each of 4 corners. Feel free to add more if you like. I left the handles on the bag in case I want to strap something else on top of the bag. I doubt I have over $15 in it and an hour of screwing around, plus I have the big cutting board left over.