Recently I wanted to buy a couple of non-standard crystals for a VLF project with the crystal divided down using a 4060 divider. After asking other people for advice it looks like Quartslab can provide the service. Individual crystals range from around £12-14 depending on frequency and type.
This is not cheap, but at least they can offer the low quantity service. There is a minimum order charge of £22.29, so I will probably order a couple of crystals for 4.59264MHz to give me a stable signal on 8.970kHz when divided by 512. The company contact is Dave Hayes G4AKY 020 7100 6357.