Hi and welcome Dominic,
Have you tried searching for products online? It's often difficult to say what products will sell for sure. It is best to do your due diligence when it comes to finding the right type of products to sell.
This is often the most common question asked by most if not all online sellers.
You can always check for the latest trends in newspapers, tv and radio
You can also check your own want list, often times what you want is also what many people are looking for.
Another area that might give you ideas, are your own hobbies.
We also have various guides to help yo come up with creative ideas on what to sell.
Hope this helps.