If you're in Canada, you're in luck. You can buy Acetazone Forte (which is chlorzoxazone plus acetaminophen) online from
Well.ca for $9.79 for 30 tablets. Acetazone Forte has 250 mg of chlorzoxazone, which is half that of Parafon Forte; you can double the dose and still stay well within the safe daily limit of acetaminophen intake. Well.ca will not ship Acetazone Forte outside of Canada, unfortunately.
The cheapest source of chlorzoxazone that I know of is
NorthWestPharmacy.com, where you can get 100 tablets of generic chlorzoxazone (500 mg each) for $35.39. This is about a sixth of what online sites typically charge. However, you need a prescription at this pharmacy.