I have a load of spare buoyancy foam if anyone is interested, 20 x 300 x 350mm sheets, each sheet will provide >1.8 kg of lift, crush depth is rated at 55 metres so well within range of recreational scuba.
Full spec on the foam can be found here:
http://www.diabgroup.com/~/media/Files/Products/Core-material-pdf/H%20March%202014%20rev12%20SI.pdf
http://www.diabgroup.com/en-GB/Markets/Subsea/Select-the-right-material-for-your-depth
£15 per sheet inc P&P in the UK
Pop me a pm if you're interested...