The silver heart design measures 10mm x 10mm (approx), and these navel rings are also available with a titanium barbell, so they might be worth a try if you have a sensitive piercing.
Bar - 1.6mm (14g) Surgical Steel
Length - 6mm (1/4"), 8mm (5/16"), 10mm (3/8") or 12mm (1/2")
Jewelled Top Ball
Design - Sterling Silver
Jewel Colour - Clear
Suitable for healed piercings only
Range - Designer Belly Bars