Philips Mycare Circular G10q LED 20W G10 Globe $58 Delivered @ Eeet5p eBay

Circular fluorescent tubes are a common light source found in oyster lights. This LED replacement from Philips allows you to upgrade to LED without replacing your entire light fitting.

Reduce total energy consumption and running costs by about 50%.
Lasts up to six times longer conventional T9 circular 32W fluoro tubes.
Install it yourself - no electrician required in most cases.
This circular LED tube uses a G10q connector (pictured above) and is ~30cm in diameter.
Circular LED Tube Installation Guide

There are two main types of existing circular fluorescent light fittings:

1) Magnetic Ballast - With Starters. These are the most common fitting type. Simply replace the tube and starter (supplied - it's a new type for LED) and you're done! These magnetic ballast fittings are identifiable by the fact they have starters present.

2) Electronic Ballast - No Starters. Unlike the example shown above, these fittings do not have a starter. These units will require an electrician to 'wire out' the existing high-frequency electronic ballast before you can install the circular LED tube.