FWIW - we have assembled a group of 7 Whisky-obsessed Canadians and have just purchased two casks from Bruichladdich. Two different barrel types and two different peating levels... and a great deal of patience as we wait for (at least) 10 years...
Here are a couple of options involving existing casks - for the impatient with deep(er) pockets:
Morrison Bowmore had offered what they called "The Individual Cask Bottling Opportunity" where they have made available a small number of specially selected Auchentoshan and Glen Garioch Casks. My information on this is from just over a year ago - so forgive me if I'm teasing you with something that is not longer available.
The promo piece I have goes on to say:
Entire Single Cask will be bottled and made exclusive to Trade Customer.
Any spirit released Aged 16 to 20 Years Old will be bottled at cask strength and presented in tube reflecting current brand identity and values.
Any spirit released Aged 21 Years and over wil be bottled at cask strength in an attractive antiqued dark brown leatherette box.
Terms of Trade:
One delivery to a single address
Lead time from receipt to actual order: approx. 8 weeks
Opportunity for small qunatity of tasting stock free of charge from final case if incomplete.
Glenfiddich will also sell mature casks; their Glenfiddich Private Vintage Program. The decision-making process involves having you select a particular vintage year from which they will provide you with samples (typically up to 10 casks to choose from). I know the owner of Willow Park in Calgary, Alberta (Wayne Henuset) went this route just this last summer and his Whisky Buyer (Dave Michiels) had the thankless job of having to fly to Scotland to laboriously and tediously wrestle with the tough tasting decision of cask selection...
We sampled the result at the November Whisky in the Warehouse event and it was very impressive.