I am having issues trying to add a zero-priced product in an Umbraco v8 / Vendr 2.4.1 project.

For this project we are allowing things like samples and brochures to be "purchased", but everything will be free, so the price will always be 0.

I get the error "Vendr.Common.Validation.ValidationException: Can't add a Product to an Order where there is no price for the Order currency." which I believe is down to the validation on the standard product adapter.

I have had a dig through the forums and the docs and I have added a custom Product adapter with no validation to try and rectify this, and added a custom class to return as an IProductSnapshot.

public class PimProductAdapter : ProductAdapterBase
{
    private readonly IUmbracoContextFactory _contextFactory;

    public PimProductAdapter(IUmbracoContextFactory contextFactory)
    {
        _contextFactory = contextFactory;
    }
    public new IProductSnapshot  GetProductSnapshot(Guid storeId, string productReference, string languageIsoCode)
    {
        using (var context = _contextFactory.EnsureUmbracoContext().UmbracoContext)
        {
            var node = context.Content
                .GetById(Guid.Parse(productReference));

            return node.GetProductSnapshot(storeId);
        }
    }

Product Snapshot:

public class PimProductSnapshot : IProductSnapshot
{
    public Guid StoreId { get; set; }
    public string ProductReference { get; set; }
    public string ProductVariantReference { get; set; }
    public string Sku { get; set; }
    public string Name { get; set; }
    public IEnumerable<AttributeCombination> Attributes { get; set; } = new List<AttributeCombination>();
    public Guid? TaxClassId { get; set; }
    public IEnumerable<ProductPrice> Prices { get; set; }
    public IDictionary<string, string> Properties { get; set; } = new Dictionary<string, string>();
    public bool IsGiftCard { get; set; }

}

and registered in the composition as so:

public class DependencyComposer : ICoreComposer
{
    public void Compose(Composition composition)
    {
        if (composition == null)
        {
            throw new ArgumentNullException(nameof(composition));
        }

        composition.RegisterUnique<IProductAdapter, PimProductAdapter>();

However I am still getting the error, and a breakpoint on the custom adapter doesn't get hit. I have also tried inheriting from IProductAdapter rather than ProductAdapterBase.

Any help on how to resolve this, or an alternative method of allowing 0 priced products would be appreciated, thanks.