To create an invoice for a non-inventory product like misc shipping, you can create a draft order in Shopify and send an invoice to your customer.

Here’s how to do it:

1. From your Shopify admin, go to Orders > Drafts

2. Click Create order

3. In the Customer section, select the customer you want to invoice.

4. To add the misc shipping charge, you can enter it as a custom line item. Click Add product then enter a name (e.g. Misc. Shipping) and a price for the shipping rate.

5. Once you have added the details, click Send invoice. This will send an invoice to your customer with a link to the checkout page where they can complete the payment.

Make sure to review the order before sending the invoice to ensure all details are correct