Hello Andy,
As Bart had mentioned, there's no quick solution to your situation, as many museum displays are custom made for the specific artifacts or designed to convey a certain story. More than likely you would need a lighting designer or a preparator who can fabricate lighting elements.
I honestly would suggest the following:
1) Reaching out to your local college/university for Interior Design, Stage Design or Film students who are about to graduate and who need experience for their thesis projects or to add to their portfolios. They can work with you to design something that could work with your budget.
2) If you are a non-profit you can reach out to contract stage designers, interior designers, electricians, showroom and gallery owners if they would be able to provide services at scale or pro bono.