We don't quite follow what you mean by "non-exempt"; could you clarify? "Create an invoice" could also describe various things, so to take a few guesses on that:
The Thank-you Page we generate for each buyer is formatted as an invoice summarizing their purchase. The Common Thank-you Email message we send each buyer normally also contains a link to that page, unless you've disabled that message or customized it to remove the
[%thankyou_link%] template tag.
You can also obtain a link to that thank-you/invoice page from your E-junkie Transaction Log, where you'd find the buyer's order and click the Copy Link button for it, then paste that link into a personal reply to the buyer.
If you just want to send someone a link to purchase a product, you can simply send them a link to your site's sales page, or copy the Text Link we provide for the product's Add to Cart, Buy Now, or Product Card button and paste that into a personal message to the buyer.
To send a link for a multi-item order, you can Add to Cart those items yourself, then click the Share icon (a sideways-V symbol) in the top-right corner of that shopping cart (next to the Cart icon) to copy a link to that order, then paste that link into a personal message to the buyer.
We also have a beta feature for creating new-order invoices, which you can find in your E-junkie Dashboard at the very bottom of the left-hand sidebar menu, under Beta Features > Create Invoice.