Millions of older and disabled people could face new restrictions on where they can go for medical equipment under a Medicare plan to overhaul how the federal insurer pays for such devices. Patients have long been able to choose any supplier, and Medicare would buy or rent the equipment based on a set schedule of fees. Now, the government plans to pay for devices sold only by approved suppliers, to be selected by competitive bidding. The change is expected to reduce costs for the government and save money for seniors. But it also may mean new hassles for patients, say suppliers and some patient-advocacy groups.