I truly hate to say this, but the simplest way to handle this is going to be to send it back to the supplier from your forwarding agent, if you can get a refund from the supplier. If you can't get it refunded, see if you can sell it to someone else as a wholesale lot, probably at a loss but at least you'll get some of the capital back out of it. Not to be negative, but you allowed yourself to fall into kind of a trap there by not being aware of the import restrictions before you tried to bring the item into the country.
I don't know why FedEx et al. would recommend a private courier -- they can't break the import restrictions any more than the big names can; they can just go in under personal exemptions. If your load is large, this means many individual shipments at probably a significant cost.