HMOs can be very picky about the type of medical equipment they'll reimburse you for. You may need to have special letters of medical necessity or pre-approval, and you'll probably have to deal with yearly deductibles or even lifetime limits on benefits.
Medicare and other government insurance policies all provide for appropriate medical equipment, particularly durable medical equipment like wheelchairs, but the rules may be even more stringent than with private health insurance, leaving you to deal with pre-approval, deductibles, annoying limits, and proofs of medical necessity.