You may want to contact DearMissMermaid.com
she knows about everything on Tortola. However she has only recently returned from an extended hospital visit and is recovering slowly but I'm sure she can point you in the right direction.
I think the hope of a rental is a bit difficult. The climate on Tortola isn't nice to things like wooden guitars on a long term basis unless well cared for daily.
I have had several guest and scheduled guest, including some Hall of Fame'rs bring down guitars on their flights. They make for some outstanding evenings at anchor
or possibly at DA Loose Mongoose some evening!
When will you be down?