Honestly for hard flooring, your best performance cleaning will be performed with straight suction and a decent bare floor brush. A generic 10" bare floor brush can be bought brand new from a vacuum store for around $10 and they are very good. You don't wheels on a bare floor brush. The best is get is something with bristles along the perimeter preferably horse hair.
Sorry to hear about your bare floor switch. I worked on a Whispertone upright years ago and the way it was designed was that the brush roll motor turned off when the height setting was changed to bare floor.
I thought these uprights were a dual motor system, with 3 position on/off switch similar to their canisters!
If you have all hard flooring and little carpet a canister vacuum is your best bet!! Do you have a canister vacuum? I have some for sale if interested and I live in central Pennsylvania.