School me in Rocker Shaft Shimming.

I'm thinking that type of shim might have to be a custom made CNC part. I've had some made on a CNC after getting some real measurement numbers for demensions off the saddles and then getting a cad drawing worked up to see exactly how things would lay out so the shims would mate perfectly to the shaft and the saddle, because I wanted a precision fit. But I have to admit, I've never seen any listed anywhere that are tapered on one side when I was researching shims for my heads. But I needed to go farther out on the valve (exhaust) instead of towards the intake side.