Robert Kennett, based in Tisbury, Wiltshire, was forced to act after an initially interested benefactor pulled out. He has only until 27 January to find a replacement.
"I need a headline sponsor, whose name would be incorporated into the show garden's title," he said. "This calls for around £17,000 investment depending on other sponsorship in kind. Other levels of support are very much open for discussion."
Kennett's garden supports Amnesty International's campaign for women's rights in Nicaragua, which has a butterfly as its emblem. His design centres on a pink cube filled with lush tropical planting and 300 butterflies.
He said the RHS and Amnesty have pledged limited funding but he still needed a lifeline. His team for the show on 3-8 July includes Greenhaven Landscapes and tropical butterfly expert Luke Brown.
Call 01747 871614 or see www.robertkennett.co.uk.