I can vouch for the AEM gauge Kenneth67 linked above as well. Works good. The housing I used was
this one from KOSO. I tried the Dakota Digital CUP-3100 first and ended up returning it. Didn't look nearly as nice as the KOSO IMO. The gauge ended up sticking outside of the cup. In the KOSO it ends up slightly recessed for a nice flush look. It is more recessed at top however due to the overhang which I think worked well in my application with the flyscreen (compliments it).