How you can build one... well, I have one (crazy) idea.
Bypass valve you and all SC owner have is held open (-> bypassing supercharger -> no boost) by vacuum. As vacuum drops close to 0, bypass starts to close and boost builds up.
Now, idea is that you add extra control to bypass vacuum input, if boost increases beyond preset limit you switch normal vacuum line to your own that starts to open bypass little bit -> boost gets no higher.
Tricky part is that there is no vacuum source when you have boost
-> electric vacuum pump?
Or you could replace bypass vacuum unit with electrical version and use electronics to close/open it... then you have total control over it.
Other idea, create a new bypass in addition of original, and install a normal turbo bypass valve (not blowoff or venting to the atmosphere). Not overly expensive but you have to create piping
Other eaton like superchargers are used somekind of dual purpose bypass to limit boost, very similar to SC original bypass but also account boost limit, not just vacuum.