Have you already got a bike with a rack at all?
If you have, I’d have thought the cheapest thing to do might be to work on making that as versatile and suitable for your particular needs as possible. Can you, for example, rig something to carry your tools upright, like a piece of drainpipe capped off at the bottom and bolted to the rack upright, or maybe experiment with running tools along the line of the bike like you might with tent poles. You can probably increase the carrying capacity of your rack quite a lot by fastening a plastic box to the top of it with pipe clips, zipties or something, or use a wire basket with a cargo net over the top. That sort of thing.
While the Dummy is fantastic, I reckon there’s a lot to be done with a regular bike and rack if you’re a bit creative with it. 🙂