Tablecloth Parasol Hole Ring

We have a couple of bistro style tables in the garden, only one of which has a table cloth.

My late wife and I had been looking for material to make a second cloth that was a close match to our 30 year old well cared for original for ages, and a couple of weeks ago I found some.

Matching the material turned out to be the easy part, trying to get a snap in ring for the parasol hole was just about impossible - Fruitless "googling" turned up a couple which were far too big for my needs but luckily I have a pair of calipers and a 3D printer...