You could edit the title to include "Sold".
I'm not sure you can delete sales threads, for obvious reasons. Whilst it may also be useful for other forum users wanting to buy/sell a similar item, as it gives an indication of value/price. ATB
Neil Price (UK Neil) makes sets of these, here's a link to a site selling his elements.
Last in the list m.Andrew Tucker 25.4mm.
He can also make anything you want as a custom job.
HTH