Ultrafin and Ultrafin Plus both have worked quite well for me. Even at slightly lower or higher than 68. The plus side for both, is that they are reasonably priced, and last for quite some time.
For one shot, Ultrafin is probably best. Ultrafin Plus can be reused. I leave the Plus on my window sill in Tupperware bottles between shots, for as much as a week or two with no issues.
Both are available throughout most of Europe, so getting them shouldn't be an issue, either.
Last edited by kintatsu; 12-04-2012 at 04:56 PM. Click to view previous post history.
Reason: Add information forgotten initially