Having a search for the adjustable version, I've just come across these LED versions too, which are a little less bulky...
Obviously find one that it compatible with your camera / lens and has good reviews... The first seems to bet the better one..
Macro Ring LED Light for Canon 1Ds,5D,7D,40D,50D,60D,500D,550D,1000D,Nikon D700,D300,D90,D60,D3,D2,D1,D7000,D5000,D3100,D3000,Olympus E620,E520,E510,E500,E420,E450,E3,E1,E-P2,Pentax,K20D,K200D/Sony Alpha A200,A230,A300,A330,A350,A380.A450,A500,A550,A700,A850,A900/SIGMA LENS with 6 FREE RINGS 49MM,55MM,58,62,67MM(UK Plug)
£31.49
http://www.amazon.co.uk/Macro-Light-Olympus-Pentax-A380-A450/dp/B003LAGNSO/ref=pd_cp_ce_1Neewer LED Macro Ring Flash FC100 For Canon Camera DSLR Canon EOS 1D/ 1Ds Series 7D/5D MarkII/60D/50D/40D/30D/20D/10D 550D/500D/450D/400D/350D/300D
£23.48
http://www.amazon.co.uk/Neewer-LED-FC100-Camera-MarkII/dp/B0050GSZCYMeiKe LED Macro Ring Flash for Nikon
£39.98
http://www.amazon.co.uk/MeiKe-Macro-Ring-Flash-Nikon/dp/B004QUZ37U/ref=pd_cp_ce_2