I've got some seepage from my brake master cylinder reservoir (Sierra), so I'm trying to find some replacement seals. Local motor factors suggest they won't be able to get them, since they're not sold separately. Any idea what I can do? Will I be able to get hold of replacements, or seal some other way? Haven't taken reservoir off yet.

If the leak is between the res' and the cylinder it might be worth pulling it out, cleaning the seals and refit. Could just be a build up of muck. Otherwise the only way to get the seals would be a full MC seal kit.