How long is too long to wait for a sales receipt?

[67XR7]

Recently purchased an automotive product and I am very happy with the service and product. But I purchased this item over two months ago with still no receipt in hand.

I have asked atleast 5x through various emails. Normally a receipt wouldn't be such an issue but I cannot come to an agreement for value with my insurance and receipts are vital to helping my case. Had my car been a 69 camaro I wouldn't have to worry about any of this. Lol

The shop is small and basically a solo operation but now it's two months later. What would you do if in my shoes?