I have a few...
I've got five that would potentially fall into that category, although some are more heavily modified than others. I have posted photos of all of these in the recent past:
Kirby G5--Renovated using an Ultimate G outer bag (the flecks of burgundy in the pattern make it look like it belongs on that machine), G4 rear handle panel, G3 cord, Sentria style brush roll. It is the most heavily modified of the lot.
Kirby Heritage 1HD--converted from dump bag setup to use disposable filter bags, including Sentria style HEPA bags, with Heritage 2/Legend 2 mini Emptor and fill tube assembly. Looks stock unless someone is familiar with Kirbys of that era.
Eureka "Ironsides" canister--The machine itself is unmodified except I bent the latch button on the hose out of the way to accommodate an Electrolux wand and power nozzle since it doesn't have one of its own. This modification uses an unmodified teal, non-telescoping 1205 style wand that has a pigtail cord at the top.
Sanitaire S645 (blue line)--renovated mostly with OEM Sanitaire parts for a red line commercial unit including larger light-gray cord hooks, a black dial-a-nap knob in place of the original light gray one (just because I had it handy and liked the look) and a generic, black 40-foot cord to replace the damaged original 30-foot gray one. Although not planned that way, the larger cord hooks came in handy for the longer cord. This one would appear pretty much stock to the untrained eye.
Sanitaire SC686 (red line)--Upgraded with an aftermarket F&G bag conversion kit and newer VGII brush roll. This one also could pass for stock, both installed with no modification to the machine.
To my mind, the Eureka is the only one of the above lot that I would actually consider to be 'bojack' since it incorporates pieces from another manufacturer and required a minor physical modification for them to fit properly. The others use original OEM parts or third party parts made to OEM specs and were fitted to the machine without any permanent physical modification (e.g., no adapters, cutting or drilling) and thus could easily be put back to their original factory configuration in a matter of minutes with no indication that they had ever been modified.