I agree embossing wheel but you can come real close with a couple of tools:
1) for the two outer borders use a stitch marker - you can even get markers that have a more square tip than pointed from CS Osborne
2) The inner section - get a piece of delrin or similar hard plastic or a brass bar of the right width and make it with two legs - i.e. a slot in the middle - start by tapping in the first two slots and then place one leg in the previous slot for the next one and so on. You can do it with just a single slot tool (I've made such from old small cold chisels ground to shape) but with the single slotter it's harder to keep the spacing even.
Layout the inner and outer borders first with a good pair of dividers, run them with the marker, and end up doing the central part. You want you cased leather a bit on the dry side rather than too wet to help retain shape.
It's a bit more time consuming than using an embossing wheel even if you could find the right one, but where there's a will there's a way.....