27.0 mm is a hard to find size. I located a seller on eBay with Kranx branded black seat posts for £15.99. It was ok as a temporary solution then upgraded to a Thomson Elite seat post costing around £100.
There’s a silver NOS DX 27.0 for sale on here but the seller is asking £60...
Four items sold. The following are still available:
(1) 1991 Marin Palisades bike
(2) 1991 Marin Muirwoods bike
(5) 1994 Marin Eldridge frame and forks
(6) 1994 Marin Eldridge frame only
(9) 199? Dirty Jo bike