what, if any, grand prixs or grand am under the hood dome lights will fit my 94 bonne?

or what buick or oldes?

Any or all could be made to fit, there is no direct fit for the bonneville, but its not that hard to come up with something that will work?

simply fabrication

what kinda fabrication are we talkign about?

Just a small bracket to hold the light, if it doesn't fit the one already there.
A piece of sheetmetal with one or two bends and two screw-holes would do it.
Ten minutes, tops. Then you attach the new bracket to the old one, and attach the light to it, and add whatever electrical connectors are needed. Shouldn't cost more than $10 including the light itself.