As @Maverick911OE stated, "Maybe have a separate member tab you can get with your member number as its own patch." might be the best/most cost effective way. Aside from the variations in the region designs, the patch embroidery would be a standard production design. A tab/rocker is an easy enough piece to produce with simple numerical text, so costs on that should be fairly reasonable as well. It will also allow for a more prominent/less cluttered design of the patch, since the member's number is now separate.
And, coming from a completely personal point of view, a unit patch with a tab/rocker is much more impressive, when compared to just a single insignia (but I'm just a beat up old Grunt, so I may be biased. Haha!)
Here's an example: