Hi CBE - I'm sorry to say I don't think the material of a hairpiece would be wearable or undetectable for daily wear as a beard. With a hairpiece the base is basically attached to your skull, which is a fixed unmoving shape, so you can put it up there and forget about it. With a full beard you would be attaching onto a very mobile area of skin, continually stretching and changing shape. I just don't think it would work. A moustache or a goatee maybe, but not a full beard. I'm not sure what to suggest - maybe a very high quality tattoo could give you the appearance of scruff.
Well, it's worth trying provided you understand the limitations. I honestly don't know whether it will work or not. I would suggest you make it in separate parts - a moustache, the goatee area and the two sideburns. You will need to make templates for them just like a hairpiece for your head, and then you can have those templates custom made. Alternatively you could try buying a stock hairpiece and cutting the shapes out, but a beard has very distinctive hair angle, lying close to the skin, different from normal head hair, so I am not sure how well that would work.
I know my hair supplier does eye brows, I can ask if they do beards. Usually the systems come in 6 inch hair length
