Because I've put hitches on all the Volvos I've owned, and because the hardware package for the hitches is no longer available from Volvo dealers, I've kept my original package (i.e., never used it) as a "reference", and attached the last two hitches I've installed using bolts from other sources (e.g., the long ones from McMaster and the shorter ones from local hardware stores).

But I've happily also fabricated spacers as well. The OEM Volvo spacers are almost precisely one inch (25mm) long. All you have to do is go to a plumbing store and get some pipe that you can cut to the right length. The only two critical specs for the pipe are an internal diameter that the bolt will fit through, and an external diameter that will allow you to slide the spacer through the bottom hole.

It's easy.

Good luck.