How can I reheat Onion Bhajis without an oven or hub to make them crispy?
If the bhajis fit into the toaster slots, toaster bags should work. They are primarily intended for toasted sandwiches, but it they can contain melted cheese good I wouldn’t expect a bit of bhaji grease to be a problem. They should work for samosas too. 
Most supermarkets sell them, there are lots of brands available on the High Street or online.