Peter, it's great that you're excited about precision riflery and getting a shooting mat. However, don't feel as though you need a shooting mat to shoot precision rifle. Lots of us use moving blankets to shoot and they work just fine.
Here's Randall shooting a match from a moving blanket:
Here's Seth shooting a match from a moving blanket:
The blanket didn't seem to impede his shooting either. Seth won that match:
One of my favorite photos from the Clinic A is this one:
That woman in the foreground brought her sporting clays vest. It worked just fine.
An open mind and an eagerness to learn will be far more important to a successful clinic experience than a dedicated shooting mat. Bring what you have to Clinic B.