ANY PPG automotive jobber or body shop with a mixing station can mix the correct color for you. AND you are going to need around a pint of color which will be around or close to $100.00 + reducer+clear+reducer for the clear etc. etc. so materials even in the small amount you will need not counting masking paper, a clean spray suit (you want to cut down on all possible dirt), some primer, some sealer and some flex additive (tourpak and saddlebags are abs and flex) some sandpaper and very quickly you have $300 + in materials. Then after it is painted and cured (natural gas to run the booth heater to cure it) More sandpaper to color sand, two or three differently aggressive pads to buff with @ $12.50 each + compound and finish glaze to finish so another $100.00 in materials. Now we get to labor @ local rate here of $48.00/hr (which is cheap) and 6 - 8 hours of actual work. So now we have $400 in materials and at least $300 in labor, probably more. $700 + tax and shop fees.
So that is a realistic reason it is cheaper to actually buy a painted tourpak from HD. And these prices are realistic, I bought a pint of color to paint the frame air deflectors on my 15 RGCVO, 1 pint and it was $81.00 out the back door and the orange for my SERG was more.
But the paint is easy to get, the rest is what is hard. And most painters want no part of it due to the fact you have to be perfect in your work, you cannot get it "close enough" and then blend surrounding areas to match like you can on a car.