Hi John,
If you can wait a short while then visit your nearest model boat show, they normally advertise in the magazines and forums. They usually start around March and you will pick up loads of items including ropes, barrels, drums, crates, buoys, buckets, crew figures etc.
Also have a look in toy shops, car boots and especially the local pound shops. If you have a spare figure, then carry him around with you and you can then check the sizes of any item you come across.
Good luck with your serach – Ken