Happy #28, Roy and Mrs. Roy! You are between silver and pearls for traditional gifts; however:

While there is no standard, traditional gift associated with the 28th anniversary, the modern theme for a 28th anniversary is orchid, the most highly coveted of ornamental plants, the delicate, exotic and graceful orchid represents love, luxury, beauty and strength. In ancient Greece, orchids were associated with virility. (Source)

Perhaps a trip to an old part of Greece might be in order?