If you have a Chippie you could do a lot worse than joining the Colchester Chipmaster land Facebook group. A very active and knowledgeable bunch and I recall a discussion on motor mounts fairly recently.

The originals are UNC threaded. I think they are male-female. They are difficult to find.

You can replace them with M12 female-female items, which are far more easily obtained.

You either have to drill out the threads in the base and use a bolt (low head) from below, or you can make a stud that has UNC threads one end to suit the imperial threads in the base and metric threads on the other to suit the metric female threads in the mount. The long bolts that come in from above need to change to metric.

These are typical of the type:

https://www.mooreinternational.co.uk/avm6045dd-m12-anti-vibration-mount-60mm-x-45mm-femalefemale

It gives a universal name for them (type C bobbin or type 3 bobbin) which might help locating other suppliers.

When I look at that page, other heights of the same diameter and thread are offered as alternatives at the borrom of the page.