Not VAT registered but some items I sell there is no VAT charged

I am not VAT registered, therefore when doing invoices or purchases VAT is included at 20%.
However, some items I buy and sell there are no VAT charged on them e.g Motorcycle helmets.
How do I set it up so that when I am doing an invoice for a motorcycle helmet the VAT can be set at 0%
If the buyer purchases additional motorcycle helmet accessories e.g a Visor, VAT is charged at 20%.
I just don’t want an invoice going out to a customer stating that VAT is charged at 20% when they have bought an item which is VAT free.

If you are not VAT registered then you do not charge VAT on anything so all sales are 0% VAT regardless.

untick VAT Registered option in account setting and you should enter purchases (inc vat) and sales as one gross amount.